feat(clients): reachability-probed presence + shareable Decky host management

Add a bounded, trust-agnostic, mDNS-INDEPENDENT QUIC reachability probe and
surface it everywhere saved-host presence is shown, so a host reached over a
routed network (Tailscale/VPN/multicast-filtering LAN) no longer reads Offline
just because it isn't advertising — the display-side companion to the 0.8.4
dial-first connect fix.

Core:
- punktfunk-core: NativeClient::probe (bounded handshake; a real host answers even
  on trust mismatch, a wrong/closed/TCP-only port fails) + punktfunk_probe C ABI
  (ABI_VERSION 3->4, header regenerated).
- pf-client-core: trust::probe_reachable_many (parallel per-host sweep).

Presence pips now read `advertising OR probed-reachable`, refreshed by a ~10-12s
background sweep off the UI thread:
- Linux (relm4): ui_hosts probed map + HostsMsg::Probed sweep.
- Windows (windows-reactor): pf-probe worker -> HostsProps.probed.
- Apple (SwiftUI): HostStore.refreshReachability, driven by HomeView + GamepadHomeView .task.
- Android (Compose): nativeProbe JNI seam + periodic LaunchedEffect (LNP-gated),
  online dot added to the touch HostCard.
- Decky already probes via --list-hosts --probe.

Decky client: make the flatpak client's known-hosts store the single source of
truth via new headless CLI modes (--list-hosts / --add-host / --set-host /
--forget-host / --reset / --reachable). The plugin can now add a host by address,
edit/forget hosts, reset all state (keeping the client identity), and shows
probe-backed online pips — state is shared with the desktop client, not duplicated.

Also lands in-progress Android 17 LNP groundwork (targetSdk 37 +
ACCESS_LOCAL_NETWORK runtime flow, permission dialogs) that was already present in
the working tree.

Verified: cargo check + clippy clean (punktfunk-core, pf-client-core, linux,
android native); android assembleDebug BUILD SUCCESSFUL; decky typecheck + rollup
build clean; probe true/false-positive behaviour exercised against a live host.
Windows and Apple were not compiled locally (no MSVC/Xcode on this Linux box).

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

clients/decky/src/index.tsx

@@ -18,10 +18,14 @@ import {
   applyUpdate,
   checkForUpdatesNow,
   hasUpdate,
-  resolvePinHost,
+  mergeHosts,
+  needsPair,
+  pinIsOnline,
   startStream,
+  toHost,
   useHosts,
   usePins,
+  useSavedHosts,
   useUpdate,
 } from "./hooks";
 import { streamPin } from "./library";
@@ -33,10 +37,18 @@ import { PairModal } from "./pair";
 // and pinned games.
 // ----------------------------------------------------------------------------------------
 const QamPanel: FC = () => {
-  const { hosts, scanning, refresh } = useHosts();
+  const { hosts: discovered, scanning, refresh: refreshDiscovered } = useHosts();
+  const { saved, loading: loadingSaved, refresh: refreshSaved } = useSavedHosts();
   const { info: update, checking, check } = useUpdate();
   const pins = usePins();
 
+  const hosts = mergeHosts(saved, discovered);
+  const busy = scanning || loadingSaved;
+  const refresh = () => {
+    void refreshDiscovered();
+    void refreshSaved();
+  };
+
   return (
     <>
       {hasUpdate(update) && (
@@ -82,12 +94,12 @@ const QamPanel: FC = () => {
       {pins.pins.length > 0 && (
         <PanelSection title="Pinned Games">
           {pins.pins.map((pin) => {
-            const { online } = resolvePinHost(pin, hosts);
+            const online = pinIsOnline(pin, hosts);
             return (
               <PanelSectionRow key={`${pin.host_fp}:${pin.game_id}`}>
                 <ButtonItem
                   layout="below"
-                  onClick={() => streamPin(pin, hosts, pins)}
+                  onClick={() => streamPin(pin, hosts.map(toHost), pins)}
                   label={pin.title}
                   description={`${pin.host_name}${online ? "" : " · offline?"}${
                     pin.paired ? "" : " · pairing required"
@@ -104,49 +116,52 @@ const QamPanel: FC = () => {
 
       <PanelSection title="Hosts">
         <PanelSectionRow>
-          <ButtonItem layout="below" onClick={refresh} disabled={scanning}>
-            {scanning ? (
+          <ButtonItem layout="below" onClick={refresh} disabled={busy}>
+            {busy ? (
               <Spinner style={{ height: "1em", marginRight: "0.5em" }} />
             ) : (
               <FaSyncAlt style={{ marginRight: "0.5em" }} />
             )}
-            {scanning ? "Scanning…" : "Refresh"}
+            {busy ? "Scanning…" : "Refresh"}
           </ButtonItem>
         </PanelSectionRow>
-        {hosts.length === 0 && scanning && (
+        {hosts.length === 0 && busy && (
           <PanelSectionRow>
             <Field focusable={false} description="Scanning your network…" />
           </PanelSectionRow>
         )}
-        {hosts.length === 0 && !scanning && (
+        {hosts.length === 0 && !busy && (
           <PanelSectionRow>
             <Field
               focusable={false}
               label="No hosts found"
-              description="Start a Punktfunk host on this network, then refresh."
+              description="Open Punktfunk to add a host by address, or start a host on this network and refresh."
             />
           </PanelSectionRow>
         )}
-        {hosts.map((h) => {
-          const needsPair = h.pair === "required" && !h.paired;
+        {hosts.map((v) => {
+          const pair = needsPair(v);
+          const h = toHost(v);
           return (
-            <PanelSectionRow key={h.fp || `${h.host}:${h.port}`}>
+            <PanelSectionRow key={v.fp || `${v.addr}:${v.port}`}>
               <ButtonItem
                 layout="below"
                 onClick={() =>
-                  needsPair
+                  pair
                     ? showModal(<PairModal host={h} onPaired={() => startStream(h)} />)
                     : startStream(h)
                 }
                 label={
                   <span style={{ display: "inline-flex", alignItems: "center", gap: "0.4em" }}>
-                    {needsPair ? <FaLock /> : <FaLockOpen />}
-                    {h.name}
+                    {pair ? <FaLock /> : <FaLockOpen />}
+                    {v.name}
                   </span>
                 }
-                description={`${h.host}:${h.port}${h.paired ? " · paired" : ""}`}
+                description={`${v.addr}:${v.port} · ${v.online ? "online" : "offline"}${
+                  pair ? " · pairing required" : v.paired ? " · paired" : ""
+                }`}
               >
-                {needsPair ? "Pair & Stream" : "Stream"}
+                {pair ? "Pair & Stream" : "Stream"}
               </ButtonItem>
             </PanelSectionRow>
           );