feat: scaffold watch-screen AI pipeline (mock-runnable skeleton)

Modular async pipeline: FrameSource->Vision->context and STT/text->Brain->TTS.
All stages are Protocols; mock backends run end-to-end with no deps/keys.
Real backends included: mss screen capture, Claude vision+brain (guarded imports).

wsai/__init__.py

@@ -0,0 +1,8 @@
+"""watch_screen_ai — an AI that watches a shared screen and talks with you."""
+
+from .config import Settings
+from .factory import build
+from .pipeline import Pipeline
+
+__all__ = ["Settings", "build", "Pipeline"]
+__version__ = "0.0.1"