Add sync-timelines: repair stale CapCut >=8.7 timeline mirror (implements fix for #35)

[renezander030]

What

Add a sync-timelines command that repairs a stale CapCut/JianYing timeline mirror, so edits made by the CLI are actually honored by the app on CapCut >= 8.7.

This is the implementation task for the bug already reported in #35. That issue documents the symptom; this one scopes the fix and is a good pickup for a contributor.

Why it matters

On CapCut >= 8.7 (seen on Windows) the app drives the timeline from template-2.tmp / draft_info.json, not draft_content.json. The CLI writes draft_content.json correctly, but the app renders from the mirror, so the edit is silently ignored. That is a data-loss-class failure: the user sees no error and no effect.

doctor already detects the condition. In src/store.ts it emits:

CapCut >= 8.7 detected without a readable template-2.tmp timeline; attach this report to issue #35.

So we detect it but have no repair path. This is the tool's last known version-compatibility gap.

Where in the code

• src/store.ts — modernStorage detection (atLeast(version, "8.7")), STANDARD_FILES (draft_content.json, draft_info.json, draft_meta_info.json, template-2.tmp), and the storage-target ordering. This is the surface the new command builds on.
• src/index.ts — command dispatch + help text (see relink as a model for a repair-style verb).
• src/command-specs.ts — register the new command spec.

Proposed approach

1. Detect the desync: load all readable storage targets, compare the timeline that the app will actually read (mirror) against draft_content.json.
2. Reconcile: write the canonical edited timeline back into every mirror target the app reads, including draft_info.json GUID reconciliation for the pre-open mirror case.
3. Refuse to run while the editor is open (reuse the existing editorProcesses() guard in src/draft.ts), with --force-write to override.
4. Keep it read-only-safe by default: print a diff/plan, apply on confirmation or --apply.

Acceptance criteria

• capcut sync-timelines <project> reconciles a draft whose template-2.tmp/draft_info.json mirror has drifted from draft_content.json.
• After running, an edit made via the CLI is visible when the project is opened in CapCut >= 8.7.
• No-op (exit 0, clear message) when targets already agree.
• Refuses to write while the editor is running unless --force-write.
• Fixture-backed test covering the drifted-mirror case.
• doctor points to sync-timelines as the remedy instead of deferring to add-video/edit changes ignored by CapCut 8.7 (Windows): timeline may be driven by template-2.tmp + draft_meta_info.json, not draft_content.json #35.

Prior art

The Davidb-2107/capcut-cli fork already ships a sync-timelines command plus draft_info.json GUID reconciliation — a good reference for the reconcile logic. See #36 for the upstreaming context.

Related: #33 (root_meta_info registration), #34 (ffprobe dimension detection). See docs/version-support.md.