feat(editor): expand details inspector sidebar (#130)

[Dyu20705]

Issue relationships

Parent issue: #128
Depends on: #129 (PR #152 merged)
Blocks: #131

Problem and scope

Implements Issue #130: Details Inspector Sidebar.

• Expands Details Inspector sidebar into a collapsible panel displaying contextual note metrics:
  • Statistics (words, characters, reading time)
  • Tags chips list (parsed via canonical parser extractTags)
  • Outgoing wiki-links list (parsed via canonical parser parseWikiLinks)
  • Backlinks list (integrated with backlinkIndex)
  • Japanese study status (read-only due date, interval, stability, difficulty)
  • Timestamps and storage metadata
• Adds editor.toggle-details command bound to Ctrl+I / Cmd+I in editor scope.
• Provides accessible keyboard focus restore and Escape dismissal.
• Ensures zero layout shift and viewport containment across 1024x768, 1280x720, 1440x900, 720x450.

Verification evidence

npm run test:content     -> PASS (3/3 passed)
npm run lint             -> PASS (0 errors, 0 warnings)
npm run test:unit        -> PASS (289/289 passed)
npm run test:integration -> PASS (107/107 passed)
npm run test:perf        -> PASS (4/4 passed)
git diff --check         -> PASS (clean)

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