macos: quit immediately when Accessibility is revoked mid-session

Even with the earlier event-tap-callback cleanup fix, revoking
Accessibility in System Settings while Lan Mouse was running with
an active capture tap could still leave system input wedged — clicks
and keypresses silently dropped until the app was force-quit.

The reliable fix is to not rely on in-process tap teardown at all.
When AX is revoked:

- The kernel guarantees an active CGEventTap is dismantled when the
  owning process exits.
- SIGINT+wait on the daemon child (main.rs already does this on
  GUI exit) drops the daemon's tap and restores the cursor.

So: continuously poll AX state (1-second GLib timer, replacing the
one-shot grant watcher), and on a revoke transition call
`app.quit()`. Input is restored within ~1-2 seconds regardless of
capture state — no force-quit required, no stuck cursor, no silently
consumed events beyond the brief window until the poller fires.

The grant-transition case is preserved: on a 0→1 flip the warning
row swaps to its "relaunch required" state, same as before.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lan-mouse-gtk/src/lib.rs

@@ -200,17 +200,31 @@ fn build_ui(app: &Application) {
         macos_status_item::setup(app, &window);
         // First-launch TCC prompts. No-op when already granted.
         macos_privacy::fire_initial_prompts();
-        // If Accessibility wasn't granted at startup, watch for the grant
-        // and switch the status row into its "relaunch required" state
-        // when it lands. The daemon subprocess initialized without AX
-        // (bailed with "accessibility permission is required") and can't
-        // recover without a restart, so a live AX toggle without a
-        // relaunch leaves the app in a broken state otherwise.
+        // Watch the Accessibility grant continuously for the lifetime
+        // of the process. On a grant, swap the warning row into its
+        // "relaunch required" state (the daemon subprocess already
+        // bailed and can't recover without a restart). On a REVOKE,
+        // quit immediately — an active CGEventTap at
+        // HeadInsertEventTap can wedge system input if the process
+        // lingers after losing AX, and forcing the process to exit is
+        // the only bulletproof way to guarantee the kernel tears the
+        // tap down.
         let window_weak = window.downgrade();
-        macos_privacy::watch_for_accessibility_grant(move || {
-            if let Some(window) = window_weak.upgrade() {
-                window.present();
-                window.refresh_capture_emulation_status();
+        let app_weak = app.downgrade();
+        macos_privacy::watch_accessibility_state(move |change| match change {
+            macos_privacy::AccessibilityChange::Granted => {
+                if let Some(window) = window_weak.upgrade() {
+                    window.present();
+                    window.refresh_capture_emulation_status();
+                }
+            }
+            macos_privacy::AccessibilityChange::Revoked => {
+                log::warn!(
+                    "Accessibility revoked — quitting to avoid wedging system input"
+                );
+                if let Some(app) = app_weak.upgrade() {
+                    app.quit();
+                }
             }
         });
     }

lan-mouse-gtk/src/macos_privacy.rs

@@ -74,29 +74,46 @@ pub fn accessibility_granted() -> bool {
 }
 
 
-/// Poll for an Accessibility grant transition. Starts a 1-second GLib
-/// timer that fires `on_granted` once, the first time
-/// `AXIsProcessTrusted()` returns true. A no-op if AX is already granted.
+pub enum AccessibilityChange {
+    /// AX was missing at startup and the user has now granted it.
+    /// Capture/emulation still need a relaunch to take effect, since
+    /// the daemon subprocess already bailed.
+    Granted,
+    /// AX was granted and the user has now revoked it. Quit immediately
+    /// — leaving the process alive with an active CGEventTap at
+    /// HeadInsertEventTap can wedge system input (clicks/keys silently
+    /// consumed) until the process dies. See
+    /// macos-cgeventtap-drop-fallthrough-tcc-revoke skill for the
+    /// underlying event-tap-disable footgun.
+    Revoked,
+}
+
+/// Poll for Accessibility grant/revoke transitions. Starts a 1-second
+/// GLib timer that fires `on_change` every time `AXIsProcessTrusted()`
+/// flips, and keeps running for the lifetime of the process.
 ///
 /// We rely on polling rather than AXObserver because the AX notification
-/// API requires a trusted process to subscribe — the precondition we're
-/// waiting for. This runs on the GTK main thread (via timeout_add_seconds_local).
-pub fn watch_for_accessibility_grant<F>(mut on_granted: F)
+/// API requires a trusted process to subscribe — the precondition we
+/// can't assume. This runs on the GTK main thread (via
+/// `timeout_add_seconds_local`).
+pub fn watch_accessibility_state<F>(mut on_change: F)
 where
-    F: FnMut() + 'static,
+    F: FnMut(AccessibilityChange) + 'static,
 {
-    if accessibility_granted() {
-        return;
-    }
-    log::info!("watching for Accessibility grant");
+    let mut last = accessibility_granted();
+    log::info!("watching Accessibility state (initial = {last})");
     glib::timeout_add_seconds_local(1, move || {
-        if accessibility_granted() {
-            log::info!("Accessibility granted; firing relaunch prompt");
-            on_granted();
-            glib::ControlFlow::Break
-        } else {
-            glib::ControlFlow::Continue
+        let current = accessibility_granted();
+        if current != last {
+            log::info!("Accessibility state flip: {last} -> {current}");
+            on_change(if current {
+                AccessibilityChange::Granted
+            } else {
+                AccessibilityChange::Revoked
+            });
+            last = current;
         }
+        glib::ControlFlow::Continue
     });
 }