fix(ui): map sensing websocket port for docker

[therahul-yo]

Summary

• Map the web UI sensing WebSocket URL from Docker HTTP port 3000 to WS port 3001.
• Preserve the Python sensing stack mapping from UI port 8080 to WS port 8765.
• Guard WebSocket event handlers against stale or unregistered connection records so late messages do not throw on lastActivity.
• Add a UI regression test covering the reported LAN/Docker port mapping.

Validation

• git diff --check
• node --check ui/services/sensing.service.js
• node --check ui/services/websocket.service.js
• node --check ui/tests/test-runner.js
• Browser UI test runner: 26/26 passed

Fixes #511

[ruvnet]

Reviewed the diff:

• buildSensingWsUrl() correctly handles the two documented deployment shapes (Docker 3000→3001, Python 8080→8765). For unrecognized HTTP ports the function falls back to window.location.host, preserving same-port behaviour for any custom setup.
• getConnection(eventName) guard in websocket.service.js is the right fix for the race where a callback fires after the connection map entry has been cleaned up. Logging the warning with url + readyState makes the symptom observable.
• New tests in test-runner.js exercise both the port-mapping logic and the cleanup race.
• Default fallback host changed from localhost:3000 to localhost:3001 — that matches the sensing-server's WS port in the Docker image, which is the right default for the demo path. Anyone running a custom HTTP+WS-on-same-port stack still works via the location fallback.

Approving + merging.