feat(editor): connect OpenCut themes media and agent edits

[sjungwon03]

Summary

• Pin reviewed Theorvane/OpenCut main merge docs: refresh OpenVideo README presentation #7 and expose four editor appearance presets, direct asset placement, and clip-focused preview.
• Keep desktop and mobile clip selection behavior on one shared timeline rule.
• Save the open timeline before side Agent turns or approved edits; its existing tools now read the live cut and their changes reload into the OpenCut-hosted editor.
• Deduplicate imported assets and recovered/generated job rows to prevent duplicate React keys.
• Enable local asset fetch and CORS for filmstrip and waveform rendering, without exposing filesystem paths.

Verification

• npm run typecheck passed.
• npm test passed: 236 files, 1,549 tests.
• npm run build passed.
• mobile/npm run typecheck passed.
• Electron under Xvfb: imported a 3-second MP4, placed two clips by double-click, selected each clip (playhead 0→3000 ms), rendered video preview, 12 filmstrip frames and 272 waveform bars, with no asset errors.
• Theorvane/OpenCut docs: refresh OpenVideo README presentation #7: approved review and CI passed before squash merge to main.

Closes #472

[sjungwon03-ai]

Review summary

Verdict: Approved

• Reviewed: OpenCut integration, timeline selection, asset protocol/CORS, Agent synchronization, and duplicate-job/asset handling
• Checks: CI terminal — verify, iOS export/module, Android module, and AI review request passed