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/__main__.py

@@ -0,0 +1,62 @@
+"""Entry point.
+
+    python -m wsai              # mock pipeline (no deps, no keys) — runs a demo
+    python -m wsai --live       # capture this screen + Claude eyes/brain
+    python -m wsai --env        # build from WSAI_* environment variables
+
+The mock run is bounded (a few frames + a scripted conversation) so it exits on
+its own; --live/--env run until Ctrl-C.
+"""
+
+from __future__ import annotations
+
+import argparse
+import asyncio
+import logging
+
+from .config import Settings
+from .factory import build
+
+
+async def _run(settings: Settings, demo: bool) -> None:
+    if demo:
+        # Bounded demo so CI / a quick check terminates.
+        from .backends.mock import MockFrameSource, MockSTT
+        from .pipeline import Pipeline
+
+        pipe = build(settings)
+        pipe.source = MockFrameSource(interval=0.3, limit=4)
+        if pipe.stt is not None:
+            pipe.stt = MockSTT(interval=0.4)
+        await pipe.run()
+        return
+    await build(settings).run()
+
+
+def main() -> None:
+    ap = argparse.ArgumentParser(prog="wsai")
+    ap.add_argument("--live", action="store_true", help="capture screen + Claude backends")
+    ap.add_argument("--env", action="store_true", help="build from WSAI_* env vars")
+    ap.add_argument("-v", "--verbose", action="store_true")
+    args = ap.parse_args()
+
+    logging.basicConfig(
+        level=logging.DEBUG if args.verbose else logging.INFO,
+        format="%(levelname)s %(name)s: %(message)s",
+    )
+
+    if args.live:
+        settings, demo = Settings.live(), False
+    elif args.env:
+        settings, demo = Settings.from_env(), False
+    else:
+        settings, demo = Settings.mock(), True
+
+    try:
+        asyncio.run(_run(settings, demo))
+    except KeyboardInterrupt:
+        pass
+
+
+if __name__ == "__main__":
+    main()