feat(android): saved-hosts list + unify trust key on address:port

A managed list of known/paired hosts on the connect screen — one-tap reconnect + forget —
and a fix for the discovered-vs-manual trust-key split.

- kit/security: KnownHostStore (replaces the fp-only PinStore) stores KnownHost{address, port,
  name, fpHex, paired} keyed by address:port, persisted as JSON in SharedPreferences. So a
  discovered and a manually-typed connection to the same host now share ONE trust record (the old
  PinStore keyed discovered hosts by the mDNS instance id, manual by host:port — pairing via one
  path wasn't seen by the other).
- MainActivity: connect() looks up trust by (address, port); on a successful TOFU or PIN pairing
  the host is saved (paired flag set for the PIN path). A "Saved hosts" section lists them (name,
  address:port · paired/trusted, fp) with tap-to-reconnect (silent, pinned) and a Forget button.

Verified live (emulator -> home-worker-2): pair -> host appears under "Saved hosts" as paired;
tap -> silent reconnect (new host session, no dialog); Forget -> removed. Trust now shared across
the discovered + manual paths by construction.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/android/app/src/main/kotlin/io/unom/punktfunk/MainActivity.kt

@@ -62,7 +62,8 @@ import io.unom.punktfunk.kit.discovery.DiscoveredHost
 import io.unom.punktfunk.kit.discovery.HostDiscovery
 import io.unom.punktfunk.kit.security.ClientIdentity
 import io.unom.punktfunk.kit.security.IdentityStore
-import io.unom.punktfunk.kit.security.PinStore
+import io.unom.punktfunk.kit.security.KnownHost
+import io.unom.punktfunk.kit.security.KnownHostStore
 import io.unom.punktfunk.kit.security.obtainIdentity
 import kotlin.math.abs
 import kotlinx.coroutines.Dispatchers
@@ -144,15 +145,15 @@ private sealed interface Screen {
 }
 
 /**
- * A trust decision awaiting the user before a connect proceeds. [hostId] is the PinStore key.
+ * A trust decision awaiting the user before a connect proceeds. [name] is the label to save the
- * Trust-on-first-use ([Kind.TRUST_NEW]) is only ever offered when the host ADVERTISED pair=optional;
+ * host under. Trust-on-first-use ([Kind.TRUST_NEW]) is only ever offered when the host ADVERTISED
- * a pair=required host or a manually-typed/unknown-policy host goes straight to PIN pairing
+ * pair=optional; a pair=required host or a manually-typed/unknown-policy host goes straight to PIN
- * ([Kind.PAIR]), and a changed fingerprint forces re-pairing — never a silent re-trust shortcut.
+ * pairing ([Kind.PAIR]), and a changed fingerprint forces re-pairing — never a silent re-trust.
  */
 private data class PendingTrust(
     val host: String,
     val port: Int,
-    val hostId: String,
+    val name: String,
     val advertisedFp: String?,
     val kind: Kind,
 ) {
@@ -206,7 +207,8 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
     }
 
     val identityStore = remember { IdentityStore(context) }
-    val pinStore = remember { PinStore(context) }
+    val knownHostStore = remember { KnownHostStore(context) }
+    var savedHosts by remember { mutableStateOf(knownHostStore.all()) }
     // Mint-once on genuine first run; an Unrecoverable store (decrypt failure) surfaces here and
     // refuses to connect — never silently shadow-minting a new identity (which would force re-pair).
     var identity by remember { mutableStateOf<ClientIdentity?>(null) }
@@ -218,11 +220,10 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
     // A trust decision awaiting the user (first-connect TOFU / fp changed / PIN pairing).
     var pendingTrust by remember { mutableStateOf<PendingTrust?>(null) }
 
-    fun hostIdFor(h2: String, p2: Int, dh: DiscoveredHost?) = dh?.key ?: "$h2:$p2"
-
     // Issue the actual connect with identity + (optional) pin. On a TOFU connect (pinHex null),
-    // persist the fingerprint the host presented so the next connect goes straight through.
+    // pin the fingerprint the host presented (as an unpaired known host) so the next connect goes
-    fun doConnect(targetHost: String, targetPort: Int, hostId: String, pinHex: String?) {
+    // straight through and it appears in the saved-hosts list.
+    fun doConnect(targetHost: String, targetPort: Int, name: String, pinHex: String?) {
         val id = identity
         if (id == null) {
             status = "Identity not ready yet — try again in a moment"
@@ -241,9 +242,11 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
             }
             connecting = false
             if (handle != 0L) {
-                if (pinHex == null) { // TOFU: pin what we observed
+                if (pinHex == null) { // TOFU: pin what we observed (unpaired)
                     val fp = NativeBridge.nativeHostFingerprint(handle)
-                    if (fp.isNotEmpty()) pinStore.pin(hostId, fp)
+                    if (fp.isNotEmpty()) {
+                        knownHostStore.save(KnownHost(targetHost, targetPort, name, fp, paired = false))
+                    }
                 }
                 onConnected(handle)
             } else {
@@ -253,28 +256,28 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
         }
     }
 
-    // Decide pinned-reconnect vs fp-changed vs TOFU vs PIN pairing before connecting. Trust-on-
+    // Decide pinned-reconnect vs fp-changed vs TOFU vs PIN pairing before connecting. Trust state is
-    // first-use is permitted ONLY when the host advertised pair=optional (dh.pairingRequired ==
+    // keyed by address:port, so a discovered and a manually-typed connection to the same host share
-    // false); a pair=required host, or a manually-typed/unknown-policy host (dh == null), must pair
+    // one record. Trust-on-first-use is permitted ONLY when the host advertised pair=optional; a
-    // by PIN — we never trust an unverified cert on faith.
+    // pair=required host, or a manual/unknown-policy host, must pair by PIN.
     fun connect(targetHost: String, targetPort: Int, dh: DiscoveredHost? = null) {
-        val hostId = hostIdFor(targetHost, targetPort, dh)
+        val known = knownHostStore.get(targetHost, targetPort)
-        val stored = pinStore.get(hostId)
         val adv = dh?.fingerprint?.lowercase()
+        val name = dh?.name ?: targetHost
         when {
             // Known host whose advertised fp still matches the pin → silent pinned reconnect.
-            stored != null && (adv == null || adv == stored) ->
+            known != null && (adv == null || adv == known.fpHex) ->
-                doConnect(targetHost, targetPort, hostId, stored)
+                doConnect(targetHost, targetPort, known.name, known.fpHex)
             // Known host whose fp changed → force re-pairing (no silent re-trust shortcut).
-            stored != null -> pendingTrust =
+            known != null -> pendingTrust =
-                PendingTrust(targetHost, targetPort, hostId, adv, PendingTrust.Kind.FP_CHANGED)
+                PendingTrust(targetHost, targetPort, known.name, adv, PendingTrust.Kind.FP_CHANGED)
             // Host explicitly advertised pair=optional → trust-on-first-use is permitted (offer it,
             // clearly labeled, alongside PIN pairing). Smart-cast: this branch ⇒ dh != null.
             dh?.pairingRequired == false -> pendingTrust =
-                PendingTrust(targetHost, targetPort, hostId, dh.fingerprint, PendingTrust.Kind.TRUST_NEW)
+                PendingTrust(targetHost, targetPort, name, dh.fingerprint, PendingTrust.Kind.TRUST_NEW)
             // pair=required, or a manual/unknown-policy host → PIN pairing is mandatory.
             else -> pendingTrust =
-                PendingTrust(targetHost, targetPort, hostId, adv, PendingTrust.Kind.PAIR)
+                PendingTrust(targetHost, targetPort, name, adv, PendingTrust.Kind.PAIR)
         }
     }
 
@@ -287,6 +290,31 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
         Text("Android client", style = MaterialTheme.typography.bodyMedium)
         Spacer(Modifier.height(24.dp))
 
+        if (savedHosts.isNotEmpty()) {
+            Text("Saved hosts", style = MaterialTheme.typography.labelLarge)
+            Spacer(Modifier.height(8.dp))
+            LazyColumn(modifier = Modifier.fillMaxWidth().heightIn(max = 220.dp)) {
+                items(savedHosts, key = { "${it.address}:${it.port}" }) { kh ->
+                    SavedHostRow(
+                        kh,
+                        enabled = !connecting,
+                        onConnect = {
+                            host = kh.address
+                            port = kh.port.toString()
+                            connect(kh.address, kh.port)
+                        },
+                        onForget = {
+                            knownHostStore.remove(kh.address, kh.port)
+                            savedHosts = knownHostStore.all()
+                        },
+                    )
+                }
+            }
+            Spacer(Modifier.height(16.dp))
+            HorizontalDivider()
+            Spacer(Modifier.height(16.dp))
+        }
+
         if (discovered.isNotEmpty()) {
             Text("Discovered hosts", style = MaterialTheme.typography.labelLarge)
             Spacer(Modifier.height(8.dp))
@@ -348,7 +376,7 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
                     }
                 },
                 confirmButton = {
-                    TextButton({ pendingTrust = null; doConnect(pt.host, pt.port, pt.hostId, null) }) {
+                    TextButton({ pendingTrust = null; doConnect(pt.host, pt.port, pt.name, null) }) {
                         Text("Trust (TOFU)")
                     }
                 },
@@ -421,9 +449,13 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit, onOpe
                                         }
                                         pairing = false
                                         if (fp.isNotEmpty()) {
-                                            pinStore.pin(pt.hostId, fp) // verified host fp; paired
+                                            // Verified host fp — save as a paired known host.
+                                            knownHostStore.save(
+                                                KnownHost(pt.host, pt.port, pt.name, fp, paired = true),
+                                            )
+                                            savedHosts = knownHostStore.all()
                                             pendingTrust = null
-                                            doConnect(pt.host, pt.port, pt.hostId, fp)
+                                            doConnect(pt.host, pt.port, pt.name, fp)
                                         } else {
                                             err = "Pairing failed — wrong PIN, or the host isn't armed."
                                         }
@@ -460,6 +492,34 @@ private fun DiscoveredHostRow(dh: DiscoveredHost, enabled: Boolean, onTap: () ->
     }
 }
 
+@Composable
+private fun SavedHostRow(
+    host: KnownHost,
+    enabled: Boolean,
+    onConnect: () -> Unit,
+    onForget: () -> Unit,
+) {
+    Card(modifier = Modifier.fillMaxWidth().padding(vertical = 4.dp)) {
+        Row(
+            modifier = Modifier.fillMaxWidth().padding(start = 12.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            Column(
+                modifier = Modifier
+                    .weight(1f)
+                    .clickable(enabled = enabled, onClick = onConnect)
+                    .padding(vertical = 12.dp),
+            ) {
+                Text(host.name, style = MaterialTheme.typography.bodyLarge)
+                val trust = if (host.paired) "paired" else "trusted (TOFU)"
+                Text("${host.address}:${host.port} · $trust", style = MaterialTheme.typography.bodySmall)
+                Text("fp ${host.fpHex.take(16)}…", style = MaterialTheme.typography.labelSmall)
+            }
+            TextButton(enabled = enabled, onClick = onForget) { Text("Forget") }
+        }
+    }
+}
+
 @Composable
 private fun StreamScreen(handle: Long, onDisconnect: () -> Unit) {
     val context = LocalContext.current

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/security/KnownHostStore.kt

@@ -0,0 +1,67 @@
+package io.unom.punktfunk.kit.security
+
+import android.content.Context
+import org.json.JSONObject
+
+/**
+ * A host the user has trusted (pinned). [fpHex] is the pinned host-cert SHA-256 (64-hex); [paired]
+ * is true when trust was established via the SPAKE2 PIN ceremony (vs trust-on-first-use).
+ */
+data class KnownHost(
+    val address: String,
+    val port: Int,
+    val name: String,
+    val fpHex: String,
+    val paired: Boolean,
+)
+
+/**
+ * Persists trusted hosts — the pinned-fingerprint store *and* the saved-hosts list — keyed by
+ * `address:port`. Replaces the old fp-only PinStore so a discovered and a manually-typed connection
+ * to the same host share one trust record (and so saved hosts can be listed + reconnected). Plain
+ * `SharedPreferences` in app-private storage: pinned fingerprints are public host identities, not
+ * secrets; the property we need is integrity, which app sandboxing provides.
+ */
+class KnownHostStore(context: Context) {
+    private val prefs =
+        context.applicationContext.getSharedPreferences("punktfunk_hosts", Context.MODE_PRIVATE)
+
+    // The pref key is just a unique id; address/port are also stored in the value so an IPv6
+    // address (which contains colons) round-trips without parsing the key.
+    private fun key(address: String, port: Int) = "$address:$port"
+
+    /** The trusted record for [address]:[port], or `null` if this host has never been trusted. */
+    fun get(address: String, port: Int): KnownHost? =
+        prefs.getString(key(address, port), null)?.let(::parse)
+
+    /** Pin (or update) a trusted host — upsert by `address:port`. */
+    fun save(host: KnownHost) {
+        val json = JSONObject()
+            .put("addr", host.address)
+            .put("port", host.port)
+            .put("name", host.name)
+            .put("fp", host.fpHex.lowercase())
+            .put("paired", host.paired)
+        prefs.edit().putString(key(host.address, host.port), json.toString()).apply()
+    }
+
+    /** Forget [address]:[port] (the next connect re-pairs / re-TOFUs). */
+    fun remove(address: String, port: Int) {
+        prefs.edit().remove(key(address, port)).apply()
+    }
+
+    /** All trusted hosts, name-sorted — backs the saved-hosts list. */
+    fun all(): List<KnownHost> =
+        prefs.all.values.mapNotNull { (it as? String)?.let(::parse) }.sortedBy { it.name.lowercase() }
+
+    private fun parse(s: String): KnownHost? = runCatching {
+        val j = JSONObject(s)
+        KnownHost(
+            address = j.getString("addr"),
+            port = j.getInt("port"),
+            name = j.getString("name"),
+            fpHex = j.getString("fp"),
+            paired = j.optBoolean("paired", false),
+        )
+    }.getOrNull()
+}

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/security/PinStore.kt

@@ -1,27 +0,0 @@
-package io.unom.punktfunk.kit.security
-
-import android.content.Context
-
-/**
- * Persists the trusted host fingerprint per host id (TOFU pinning / completed pairing). Keyed by the
- * mDNS instance id (`DiscoveredHost.key`) or `"host:port"` for a manually-typed host. Values are
- * lowercase 64-hex SHA-256. Plain `SharedPreferences` in app-private storage — pins are not secrets
- * (they're public host fingerprints); the security property is integrity, which app sandboxing gives.
- */
-class PinStore(context: Context) {
-    private val prefs =
-        context.applicationContext.getSharedPreferences("punktfunk_pins", Context.MODE_PRIVATE)
-
-    /** The pinned fingerprint for [hostId], or `null` if this host has never been trusted. */
-    fun get(hostId: String): String? = prefs.getString(hostId, null)
-
-    /** Pin (or re-pin) [hostId] to [fpHex]. Normalizes to lowercase. */
-    fun pin(hostId: String, fpHex: String) {
-        prefs.edit().putString(hostId, fpHex.lowercase()).apply()
-    }
-
-    /** Forget [hostId]'s pin (so the next connect re-TOFUs / re-pairs). */
-    fun remove(hostId: String) {
-        prefs.edit().remove(hostId).apply()
-    }
-}