feat: add accessibility-based agent state detector

Adapted from plan to match real a11y tree structure: Electron web
content exposes in-app buttons as AXStaticText values, not AXButton
titles. Detects via exact matches and regex patterns. Uses correct
Cursor bundle ID for process lookup.

Made-with: Cursor

tests/test_detector.py

@@ -0,0 +1,72 @@
+import pytest
+from unittest.mock import patch, MagicMock
+from cursor_flasher.detector import (
+    CursorDetector,
+    parse_ui_signals,
+    UISignals,
+)
+
+
+class TestParseUISignals:
+    def test_no_elements_means_no_signals(self):
+        signals = parse_ui_signals([])
+        assert signals.agent_working is False
+        assert signals.approval_needed is False
+
+    def test_stop_text_means_agent_working(self):
+        elements = [{"role": "AXStaticText", "value": "Stop"}]
+        signals = parse_ui_signals(elements)
+        assert signals.agent_working is True
+
+    def test_cancel_generating_means_agent_working(self):
+        elements = [{"role": "AXStaticText", "value": "Cancel generating"}]
+        signals = parse_ui_signals(elements)
+        assert signals.agent_working is True
+
+    def test_accept_text_means_approval_needed(self):
+        elements = [{"role": "AXStaticText", "value": "Accept"}]
+        signals = parse_ui_signals(elements)
+        assert signals.approval_needed is True
+
+    def test_reject_text_means_approval_needed(self):
+        elements = [{"role": "AXStaticText", "value": "Reject"}]
+        signals = parse_ui_signals(elements)
+        assert signals.approval_needed is True
+
+    def test_run_this_time_means_approval_needed(self):
+        elements = [{"role": "AXStaticText", "value": "Run this time only (⏎)"}]
+        signals = parse_ui_signals(elements)
+        assert signals.approval_needed is True
+
+    def test_both_signals(self):
+        elements = [
+            {"role": "AXStaticText", "value": "Stop"},
+            {"role": "AXStaticText", "value": "Accept"},
+        ]
+        signals = parse_ui_signals(elements)
+        assert signals.agent_working is True
+        assert signals.approval_needed is True
+
+    def test_irrelevant_text_ignored(self):
+        elements = [{"role": "AXStaticText", "value": "Settings"}]
+        signals = parse_ui_signals(elements)
+        assert signals.agent_working is False
+        assert signals.approval_needed is False
+
+    def test_button_role_also_detected(self):
+        elements = [{"role": "AXButton", "title": "Accept"}]
+        signals = parse_ui_signals(elements)
+        assert signals.approval_needed is True
+
+    def test_partial_match_on_run_command(self):
+        elements = [{"role": "AXStaticText", "value": "Run command"}]
+        signals = parse_ui_signals(elements)
+        assert signals.approval_needed is True
+
+
+class TestCursorDetector:
+    def test_returns_none_when_cursor_not_running(self):
+        detector = CursorDetector()
+        with patch.object(detector, "_find_cursor_pid", return_value=None):
+            signals = detector.poll()
+            assert signals is None