Add PantheonClaw integration

[Starlitnightly]

feat: PantheonClaw gateway integration

Introduces PantheonClaw, a multi-channel mobile gateway layer that routes
messages from Slack, Telegram, Discord, WeChat, Feishu, QQ, and iMessage
into Pantheon's existing chatroom and agent runtime.

New module: pantheon/claw/

• bridge.py — ChatRoomGatewayBridge maps incoming gateway sessions to
  Pantheon chat rooms and streams agent responses back to the originating channel
• manager.py — GatewayChannelManager starts/stops each channel in its own
  daemon thread, maintains per-channel log buffers, and exposes state for the UI
• registry.py — ClawRouteRegistry tracks active ConversationRoute mappings
• runtime.py — shared ChannelRuntime base with queuing, dedup, and
  chunk/step callback helpers
• config.py — ClawConfigStore with masked-value serialization for secrets
• channels/ — full implementations for Slack, Telegram, Discord, WeChat,
  Feishu, QQ, and iMessage

WeChat QR login

• manager.py exposes wechat_get_login_qr() and wechat_poll_login_status()
• room.py adds @tool methods wechat_login_qr and wechat_login_status
  using asyncio.to_thread() to avoid blocking the agent event loop

Feishu WebSocket fix

• lark_oapi/ws/client.py captures asyncio.get_event_loop() at module-import
  time as a module-level global. When the module is first imported inside
  asyncio.run(), that variable holds the already-running loop, causing every
  subsequent loop.run_until_complete() call to raise
  "This event loop is already running"
• Fix: ws_client creation (including EventDispatcherHandler.builder and
  lark.ws.Client) is moved inside run_ws(), a plain daemon thread with no
  running event loop. Before calling start(), the module-level loop variable
  is overwritten with asyncio.new_event_loop() so lark_oapi gets a fresh loop
  it can call run_until_complete() on
• Stop path calls asyncio.run(ws_client._disconnect()) for clean teardown,
  matching the reference implementation in OmicClaw

Other

• Added optional dependency group claw in pyproject.toml
• Updated Dockerfile and docs to reference the new group
• Added tests/test_claw_gateway.py