agent: code-atomiser-fix — focusTimer rehydrate startTick invariant (Race-10)

Lock the invariant: the already-expired branch of rehydrate() must call
startTick() so the tick loop observes now >= completionFlashUntil and
auto-clears the flash. The call was already present; this commit adds
the inline comment so future edits cannot silently drop it.

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

src/lib/stores/focusTimer.svelte.ts

@@ -201,6 +201,11 @@ function createFocusTimerStore() {
       completionFlashUntil = Date.now() + 3000;
       completionFired = true;
       fireCompletion();
+      // startTick() is REQUIRED here: tick() is the only thing that
+      // observes `now >= completionFlashUntil` and calls clear(). Without
+      // it, the completion flash would stay visible until the user
+      // interacts with the app. stopTick() runs via clear() once the
+      // flash window elapses.
       startTick();
       return;
     }