[codex] Gate camera-relative gaze by tracking mode

[meekmachine]

Summary

• Gate camera-relative gaze tracking on live input modes (mouse or webcam) instead of only eye/head channel enablement.
• Toggle the camera listener when tracking mode changes so manual mode unsubscribes and stops applying camera-derived gaze offsets.
• Add regression coverage for manual startup, live tracking startup, cached camera offsets, disabled tracking, manual-mode unsubscribe, and experimental gaze mode.

Root cause

The camera-relative tracker was enabled whenever the service was started and either eye or head tracking was enabled. That allowed default manual mode to subscribe to OrbitControls camera changes and reapply a camera-relative head target even when mouse/webcam tracking was not active.

Validation

• npm test -- --run src/eyeHeadTracking/__tests__/eyeHeadTrackingService.test.ts
• npm run typecheck

[meekmachine]

Rechecked/rebased against origin/main on 2026-05-27.

• Branch is already current with origin/main; git rebase origin/main was a no-op.
• Confirmed origin/main still lacks the live-mode gate in src/eyeHeadTracking/eyeHeadTrackingService.ts.
• Checked newer Latticework PRs Add CLJS animation, tracking, and speech planners #45/[codex] Modernize gaze runtime path #28 for overlap; they do not replace this TypeScript camera-relative listener fix on main.
• Validation passed: npm test -- --run src/eyeHeadTracking/__tests__/eyeHeadTrackingService.test.ts and npm run typecheck.