feat: implement spatial quick actions context menu for 3D scene
Implements right-click and long-press context menus for all 3D elements:
- Raycasting with priority order: tracks > nodes > zones > portals > triggers > ground
- Context menu renders in under 50ms with intelligent viewport positioning
- Element-specific actions:
* Tracks: identify, follow camera, view history, false positive, explain, set unknown
* Nodes: edit label, health details, OTA update, blink LED, reassign role, remove
* Zones: edit bounds, rename, occupancy history, automation, delete
* Empty space: add virtual node, create zone, set home point, place portal
* Portals: edit, crossing history, delete
* Triggers: edit, test fire, toggle enable, delete
Follow camera mode:
- Smooth interpolation using VectorLerp (default 3m behind, 2m above)
- "Following: [Person]" chip with unfollow button
- Scroll wheel zoom adjustment during follow
- Auto-exit when track deleted or becomes DELETED state
- OrbitControls disabled during follow mode
Tests: 22 tests covering raycasting, menu items, follow mode,
dismissal behavior, action execution, and performance.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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