refactor `src/components/viewer/ViewerCanvas.svelte`

[jwt625]

[jwt625]

and probably also src/lib/renderer/PixiRenderer.ts

[jwt625]

Refactor Update: ViewerCanvas.svelte

Summary

Refactor is in progress and behavior-preserving so far. The goal is to make ViewerCanvas orchestration-only by extracting focused controllers/helpers.

Completed

• Extracted keyboard mode logic to src/lib/viewer/ViewerKeyModeController.ts
• Extracted collaboration callback registration to src/lib/viewer/setupViewerCollabSync.ts
• Extracted measurement input handling to src/lib/viewer/ViewerMeasurementController.ts
• Extracted comment placement/submission/recenter logic to src/lib/viewer/ViewerCommentController.ts
• Extracted renderer bootstrap/init flow to src/lib/viewer/initializeViewerRenderer.ts
• Updated src/components/viewer/ViewerCanvas.svelte to delegate to the extracted modules

Validation

• Targeted test runs are passing (including collaboration/viewport suites)
• pnpm check still reports one pre-existing unrelated issue:
  • src/lib/renderer/overlays/MeasurementOverlay.ts:19 (app is declared but never read)

Next Steps

• Extract remaining viewport sync orchestration from ViewerCanvas
• Optionally extract remaining UI wiring/toggle logic
• Run final validation pass after refactor completion