feat(clients): signal explicit exit (QUIT_CLOSE_CODE) on deliberate disconnect

The core's deliberate-quit close (NativeClient::disconnect_quit → QUIT_CLOSE_CODE,
host skips the keep-alive linger) was implemented but never called by any client.
Wire it to each client's explicit user-disconnect action — NOT to a network drop /
host-ended / app-background (those keep the linger for a reconnect):

- core: new C-ABI punktfunk_connection_disconnect_quit(c) for the ABI clients
- Linux (direct-core): Ctrl+Alt+Shift+D + the controller escape chord
- Windows (direct-core): Ctrl+Alt+Shift+D
- Apple (C-ABI): PunktfunkConnection.disconnectQuit() + a `deliberate` flag on
  SessionModel.disconnect() (sessionEnded passes false → keeps the linger)
- Android (JNI): new nativeDisconnectQuit export, called from the back gesture +
  the Select+Start+L1+R1 chord (not the host-gone watchdog)
- probe already did this via --quit (b71dc94)

Verified: core + Linux client + Android (cargo-ndk + gradle) build clean;
Windows/Apple compile-checked by CI.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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

@@ -150,7 +150,9 @@ fun StreamScreen(handle: Long, micEnabled: Boolean, onDisconnect: () -> Unit) {
         activity?.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE
         activity?.streamHandle = handle // route hardware keys to this session
         activity?.axisMapper = Gamepad.AxisMapper(handle) // route joystick axes
-        activity?.requestStreamExit = onDisconnect // Select+Start+L1+R1 chord leaves the stream
+        // Select+Start+L1+R1 chord leaves the stream — a deliberate quit (signal it so the host skips
+        // the keep-alive linger), unlike a host-ended / backgrounded drop.
+        activity?.requestStreamExit = { NativeBridge.nativeDisconnectQuit(handle); onDisconnect() }
         activity?.setConsoleHighRefreshRate(false) // let the decoder's setFrameRate pick the panel rate
         // Host→client feedback (rumble + DualSense lightbar/LEDs); poll threads stopped before close.
         val feedback = GamepadFeedback(handle).also { it.start() }
@@ -179,7 +181,8 @@ fun StreamScreen(handle: Long, micEnabled: Boolean, onDisconnect: () -> Unit) {
         }
     }
 
-    BackHandler { onDisconnect() }
+    // Back gesture = a deliberate exit → signal the quit so the host tears down now (no linger).
+    BackHandler { NativeBridge.nativeDisconnectQuit(handle); onDisconnect() }
 
     Box(modifier = Modifier.fillMaxSize()) {
         AndroidView(

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

@@ -82,6 +82,14 @@ object NativeBridge {
         name: String,
     ): String
 
+    /**
+     * Signal a **deliberate** user disconnect on [handle] before [nativeClose]: the session closes
+     * with `QUIT_CLOSE_CODE` so the host tears it down immediately instead of holding the keep-alive
+     * linger for a reconnect. Call from an explicit disconnect gesture only — NOT from a
+     * host-ended/network-drop end or an app-background (those keep the linger). No-op on `0`.
+     */
+    external fun nativeDisconnectQuit(handle: Long)
+
     /** Tear down a session handle returned by [nativeConnect]. No-op on `0`. */
     external fun nativeClose(handle: Long)
 

clients/android/native/src/session/connect.rs

@@ -179,6 +179,30 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeClose(
     })
 }
 
+/// `NativeBridge.nativeDisconnectQuit(handle)` — signal a DELIBERATE user quit before `nativeClose`,
+/// so the session closes with `QUIT_CLOSE_CODE` and the host tears it down immediately instead of
+/// holding the keep-alive linger for a reconnect. Call from an explicit disconnect action only (a
+/// plain drop / app-background keeps the linger). The handle is only BORROWED (not freed). No-op on `0`.
+///
+/// # Safety contract
+/// `handle` must be `0` or a live handle from [`Java_io_unom_punktfunk_kit_NativeBridge_nativeConnect`],
+/// not freed / closed concurrently with this call (Kotlin still owns it and closes it via `nativeClose`).
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeDisconnectQuit(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+) {
+    jni_guard((), || {
+        if handle != 0 {
+            // SAFETY: per the contract, `handle` is a live `Box<SessionHandle>` — we only borrow it
+            // (no drop), so it stays owned by Kotlin for the later `nativeClose`.
+            let sh = unsafe { &*(handle as *const SessionHandle) };
+            sh.client.disconnect_quit();
+        }
+    })
+}
+
 /// `NativeBridge.nativeHostFingerprint(handle): String` — the SHA-256 (64-hex) of the cert the host
 /// presented on this connection. Valid after a successful `nativeConnect`; Kotlin pins it on a TOFU
 /// connect. `""` on a `0` handle.

clients/apple/Sources/PunktfunkClient/Session/SessionModel.swift

@@ -276,7 +276,10 @@ final class SessionModel: ObservableObject {
         disconnect()
     }
 
-    func disconnect() {
+    /// Tear the session down. `deliberate` (the default) means a user-initiated quit — signal
+    /// `disconnectQuit()` so the host skips the keep-alive linger; `sessionEnded()` (a host-ended /
+    /// dropped session) passes `false` to leave the linger intact.
+    func disconnect(deliberate: Bool = true) {
         statsTimer?.invalidate()
         statsTimer = nil
         let audio = self.audio
@@ -294,6 +297,8 @@ final class SessionModel: ObservableObject {
             Task.detached {
                 audio?.stop()
                 feedback?.stop()
+                // Deliberate user quit → tell the host to skip the keep-alive linger (must precede close).
+                if deliberate { conn.disconnectQuit() }
                 conn.close()
             }
         } else {
@@ -321,7 +326,7 @@ final class SessionModel: ObservableObject {
     func sessionEnded() {
         guard connection != nil else { return }
         let name = activeHost?.displayName ?? "host"
-        disconnect()
+        disconnect(deliberate: false) // host/network ended it — keep the linger for a reconnect
         errorMessage = "Session ended by \(name)."
     }
 

clients/apple/Sources/PunktfunkKit/Connection/PunktfunkConnection.swift

@@ -759,6 +759,17 @@ public final class PunktfunkConnection {
         _ = punktfunk_connection_send_input(h, &ev)
     }
 
+    /// Signal a **deliberate** user-initiated quit before ``close()``: the connection closes with
+    /// `QUIT_CLOSE_CODE` (81) so the host tears the session down immediately instead of holding the
+    /// keep-alive linger for a reconnect. Call only from an explicit "Disconnect" action — NOT from a
+    /// network drop / host-ended / app-background (those keep the linger). Idempotent, safe pre-close.
+    public func disconnectQuit() {
+        abiLock.lock()
+        defer { abiLock.unlock() }
+        guard let h = handle, !closeRequested else { return }
+        punktfunk_connection_disconnect_quit(h)
+    }
+
     /// Close the connection and free the handle. Safe from any thread, idempotent; waits
     /// for in-flight pulls (≤ their timeouts) before tearing down.
     public func close() {

clients/linux/src/ui_stream.rs

@@ -817,6 +817,9 @@ fn attach_keyboard(
         // the capture toggle alone can't end a stream, so this is the keyboard's explicit exit.
         if state.contains(chord) && keyval.to_lower() == gdk::Key::d {
             cap.release();
+            // Deliberate user exit → close with QUIT_CLOSE_CODE so the host tears the session down
+            // immediately instead of holding the keep-alive linger for a reconnect.
+            cap.connector.disconnect_quit();
             stop_kb.store(true, Ordering::SeqCst);
             return glib::Propagation::Stop;
         }
@@ -1024,6 +1027,8 @@ fn spawn_disconnect_watch(
     glib::spawn_future_local(async move {
         if disconnect_rx.recv().await.is_ok() {
             cap.release();
+            // Deliberate user exit (the controller escape chord) → QUIT_CLOSE_CODE, host skips linger.
+            cap.connector.disconnect_quit();
             if window.is_fullscreen() {
                 window.unfullscreen();
             }

clients/windows/src/input.rs

@@ -281,6 +281,9 @@ unsafe extern "system" fn kbd_proc(code: i32, wparam: WPARAM, lparam: LPARAM) ->
                 // the cursor is free while the session winds down and the UI navigates home.
                 if !up && vk == VK_D.0 && st.ctrl && st.alt && st.shift {
                     set_captured(st, false);
+                    // Deliberate user exit → close with QUIT_CLOSE_CODE so the host tears the session
+                    // down immediately instead of holding the keep-alive linger for a reconnect.
+                    st.connector.disconnect_quit();
                     st.stop.store(true, Ordering::SeqCst);
                     tracing::info!("disconnect requested (Ctrl+Alt+Shift+D)");
                     return LRESULT(1);

crates/punktfunk-core/src/abi.rs

@@ -2432,6 +2432,22 @@ pub unsafe extern "C" fn punktfunk_connection_probe_result(
     })
 }
 
+/// Signal a **deliberate quit** (a user "stop", not a network drop) before closing: the connection
+/// closes with [`QUIT_CLOSE_CODE`] instead of code 0, so the host tears the session down immediately
+/// (skips the keep-alive linger) rather than holding it for a reconnect. Call this right before
+/// [`punktfunk_connection_close`] on a user-initiated disconnect; a plain close (network drop,
+/// backgrounding) leaves the linger intact. NULL is a no-op.
+///
+/// # Safety
+/// `c` was returned by [`punktfunk_connect`] and remains valid (closed via `punktfunk_connection_close`).
+#[cfg(feature = "quic")]
+#[no_mangle]
+pub unsafe extern "C" fn punktfunk_connection_disconnect_quit(c: *mut PunktfunkConnection) {
+    if let Some(c) = unsafe { c.as_ref() } {
+        c.inner.disconnect_quit();
+    }
+}
+
 /// Close the connection and free the handle (joins the internal threads). NULL is a no-op.
 ///
 /// # Safety

include/punktfunk_core.h

@@ -1501,6 +1501,18 @@ PunktfunkStatus punktfunk_connection_probe_result(const PunktfunkConnection *c,
                                                   PunktfunkProbeResult *out);
 #endif
 
+#if defined(PUNKTFUNK_FEATURE_QUIC)
+// Signal a **deliberate quit** (a user "stop", not a network drop) before closing: the connection
+// closes with [`QUIT_CLOSE_CODE`] instead of code 0, so the host tears the session down immediately
+// (skips the keep-alive linger) rather than holding it for a reconnect. Call this right before
+// [`punktfunk_connection_close`] on a user-initiated disconnect; a plain close (network drop,
+// backgrounding) leaves the linger intact. NULL is a no-op.
+//
+// # Safety
+// `c` was returned by [`punktfunk_connect`] and remains valid (closed via `punktfunk_connection_close`).
+void punktfunk_connection_disconnect_quit(PunktfunkConnection *c);
+#endif
+
 #if defined(PUNKTFUNK_FEATURE_QUIC)
 // Close the connection and free the handle (joins the internal threads). NULL is a no-op.
 //