fix(mobile): announce the stale-status swap and pin the hold's cancel path

The row rewrites itself from "Agent is working" to "Agent status stale"
with no live region, so screen-reader users got no cue for the exact
state this change exists to communicate (WCAG 2.1 SC 4.1.3). Matches the
send-error banner's existing pattern in this view.

Also covers the anti-flicker guarantee itself: a link that recovers
inside the 600ms hold must cancel the armed timer, not merely lose the
race with it.

mobile/src/session/MobileAgentWorkingIndicator.tsx

@@ -41,7 +41,9 @@ export function MobileAgentWorkingIndicator({
   return (
     // Not dimmed: the label is the only thing left carrying the state once the
     // dots go, and fading it under `textMuted` drops it below AA on `bgBase`.
-    <View style={styles.row}>
+    // The live region is constant, not toggled with `stale` — Android only
+    // announces content changes once the mode is already set.
+    <View style={styles.row} accessibilityLiveRegion="polite">
       <Text style={styles.label}>{stale ? 'Agent status stale' : 'Agent is working'}</Text>
       {stale ? null : (
         <View style={styles.dots}>

mobile/src/session/MobileNativeChatView.test.ts

@@ -252,6 +252,22 @@ describe('MobileNativeChatView', () => {
     expect(stopButton().props.disabled).toBe(true)
   })
 
+  it('never goes stale when the link recovers inside the hold', async () => {
+    vi.useFakeTimers()
+    await render({ agentWorking: true, inputLockReason: 'disconnected' })
+
+    await act(async () => {
+      await vi.advanceTimersByTimeAsync(300)
+    })
+    await relock('waiting')
+    await settleLockDebounce()
+
+    // The armed timer has to be cancelled, not just overruled — a surviving one
+    // would fire late and mute a row whose transport is already back.
+    expect(workingIndicator().props.stale).toBe(false)
+    expect(stopButton().props.disabled).toBe(false)
+  })
+
   it('restores a live Stop as soon as the transport reconnects', async () => {
     vi.useFakeTimers()
     await render({ agentWorking: true, inputLockReason: 'disconnected' })