fix(editor): reset camera state on dispose to prevent stuck 'moving' state (tldraw#8396)

Fixes tldraw#8386

When using deep links with React strict mode (or any scenario where the
editor is disposed mid-camera-transition), the camera state can get
permanently stuck at `'moving'`. This keeps the `tl-hit-test-blocker`
div covering the entire canvas with `pointer-events: all`, blocking all
shape interactions (resize, rotate, select, etc.).

**Root cause:** When the editor is disposed, `TickManager.dispose()`
stops the tick loop, but the camera decay callback (subscribed to the
`'tick'` event) never fires, leaving `cameraState` stuck at `'moving'`
in the shared store. The next editor instance inherits this stale state.

**Fix:** Add a disposable that resets `cameraState` to `'idle'` and
unsubscribes the decay callback when the editor is torn down. This
follows the React cleanup pattern — each editor instance properly cleans
up its transient state on dispose.

### Change type

- [x] `bugfix`

### Test plan

1. In `apps/examples/src/index.tsx`, set `ENABLE_STRICT_MODE = true`
2. Run `yarn dev`, go to
`http://localhost:5420/configuration/deep-links/full`
3. Draw a shape → verify resize/rotate handles work (cursor changes on
hover, can drag)
4. Copy a deep link, move camera, paste the deep link URL
5. Verify handles still work after navigation
6. Verify `editor.getCameraState()` returns `'idle'` after navigation
completes

To reproduce the bug on `main`:
1. Set `ENABLE_STRICT_MODE = true` in `apps/examples/src/index.tsx`
2. Run `yarn dev`, go to
`http://localhost:5420/configuration/deep-links/full`
3. Draw a shape → resize/rotate handles will NOT work (cursor doesn't
change, can't drag)
4. `editor.getCameraState()` returns `'moving'` and never transitions to
`'idle'`

- [ ] Unit tests
- [ ] End to end tests

### Release notes

- Fixed camera state getting stuck at 'moving' when using deep links
with React strict mode, which blocked all pointer interactions on the
canvas.

### Code changes

| Section    | LOC change |
| ---------- | ---------- |
| Core code  | +6 / -0    |

Author: MitjaBezensek

packages/editor/src/lib/editor/Editor.ts

@@ -361,6 +361,12 @@ export class Editor extends EventEmitter<TLEventMap> {
 		this.fonts = new FontManager(this, fontAssetUrls)
 
 		this._tickManager = new TickManager(this)
+		this.disposables.add(() => {
+			// Reset camera state to 'idle' so the store isn't left stuck at 'moving'
+			// when tick events stop (e.g. React strict mode disposes while camera is moving)
+			this.off('tick', this._decayCameraStateTimeout)
+			this._setCameraState('idle')
+		})
 
 		this.inputs = new InputsManager(this)