Add web-client pointer-lock mouse capture and serial bridge to MacFriends Arduino

[h4rm0n1c]

Motivation

• Enable the web UI to drive the MacFriends Arduino ADB core so browser pointer motion and clicks control the Macintosh via the existing Arduino firmware.
• Keep the transport byte-for-byte compatible with the MacFriends host client so firmware expectations are preserved (magic=123, updateType/mouse layout, dx/dy clamped).

Description

• Add AdbSerialBridge to client_web/src/ebd_ipkvm_web/app.py which discovers /dev/serial/by-id/usb-FTDI_FT232R_USB_UART_*-if00-port0 by default (override via ADB_SERIAL_PORT), opens it at 115200, and exposes connect, send_mouse, and close helpers.
• Wire the bridge into SessionManager so the serial device is opened on session start and closed on session stop/disconnect, and handle incoming WebSocket mouse_input messages by forwarding them to the serial bridge.
• Implement browser pointer-lock capture in client_web/src/ebd_ipkvm_web/static/index.html to accumulate relative dx/dy and left-button state and send mouse_input over the WebSocket (safety mouse-up on unlock).
• Document the serial packet format and usage in client_web/README.md and docs/protocol/adb.md, and add brief entries to docs/agent/log.md, docs/agent/decisions.md, and docs/agent/notes.md describing the change and pointer-lock caveat.

Testing

• Created an editable venv and installed dependencies with pip install -e . which succeeded.
• Compiled the web package with python -m compileall src/ebd_ipkvm_web and successfully imported create_app via python -c "from ebd_ipkvm_web.app import create_app; app=create_app()".
• Validated the serial packet layout size via struct.calcsize('<bBbbbBBB') to confirm the runtime packet length.
• Ran the web server (python -m ebd_ipkvm_web) and performed a browser smoke check with Playwright to render the UI (server started cleanly and screenshot captured).

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Codex Task