fix: prevent false positives from stale approval buttons in chat history

State machine no longer transitions directly from IDLE to WAITING_FOR_USER
on approval signals. Must see AGENT_WORKING first — this prevents stale
buttons like "Run this time only" persisting in chat history from
triggering the flash when no agent task is active.

Also removed "Continue" and "Resume" from approval keywords (too generic,
appear in normal chat text).

Made-with: Cursor

tests/test_state.py

@@ -66,10 +66,17 @@ class TestStateMachine:
         changed = sm.update(agent_working=False, approval_needed=False)
         assert sm.cooldown == 5.0
 
-    def test_direct_approval_from_idle(self):
-        """If we detect approval buttons without seeing agent_working first,
-        still transition to WAITING_FOR_USER."""
+    def test_stale_approval_from_idle_ignored(self):
+        """Approval buttons in IDLE state (stale chat history) must not trigger flash."""
         sm = StateMachine()
         changed = sm.update(agent_working=False, approval_needed=True)
+        assert sm.state == FlasherState.IDLE
+        assert changed is False
+
+    def test_approval_after_working_triggers(self):
+        """Approval buttons after seeing agent work should trigger flash."""
+        sm = StateMachine()
+        sm.update(agent_working=True, approval_needed=False)
+        changed = sm.update(agent_working=False, approval_needed=True)
         assert sm.state == FlasherState.WAITING_FOR_USER
         assert changed is True