Enhancement: Migrate sync state on git rename to avoid duplicate Notion pages

[virtualguard101]

Summary

When a nav-listed file is renamed or moved (git mv), incremental sync treats the new path as a create and leaves the old file_rel entry in .notion_sync_state.json. This produces duplicate Notion pages for the same note.

Current behavior

git_diff correctly records rename status (R100\told\tnew):

• Old path → md_deleted (logged; Notion page untouched)
• New path → md_changed → sync_one_page creates a new page

State is keyed by file_rel, so the old mapping is never migrated to the new key.

Proposed solution

1. On rename entries in git diff, migrate state: state.pages[old_rel] → state.pages[new_rel] (same Notion id / url).
2. Optionally reparent if nav parent changed as part of the move.
3. Update content on the existing Notion page instead of creating a new one.
4. Log: renamed state obsidian/old.md → obsidian/new.md.

Also handle renames passed via --paths / CI path lists when old path appears in md_deleted and new in md_changed in the same run.

Acceptance criteria

• git mv of a synced note updates content on the existing Notion page.
• No second page created for the new file_rel.
• Old state key removed after migration.
• Dry-run reports state migration.
• Works with structure reconciliation when parent section also changes.

Related

• Nav hierarchy reconciliation (reparent)
• Opt-in orphan pruning (old path without migration would leave orphan)