T1: Test foundation — pytest suite with fake sinks #7

Parent

#6

What to build

Promote scripts/smoke.py into a proper pytest-asyncio test suite under tests/. The suite tests the daemon's observable behaviour at the WebSocket boundary — a fake WS client connects, sends messages, and asserts daemon responses and side effects via fake sinks.

Add FakePointerSink (records emitted pointer/key events), extend the existing FakeScrollSink, and add FakeFocusBackend (an async iterator that tests drive by pushing AppInfo values). All subsequent tickets add their assertions here.

Acceptance criteria

• tests/ directory exists with pytest-asyncio configured
• Existing smoke coverage (server startup, layout push on connect, button press → shell dispatch, jog → scroll, page navigation, layout reload) passes as pytest tests
• FakePointerSink, FakeScrollSink, and FakeFocusBackend are importable test fixtures
• just test (or equivalent) runs the suite and exits green

Blocked by

None — can start immediately.