Show citation context and navigate to occurrences

[aidenlx]

Parent

#689

What to build

Add enough source context and navigation to make each cited-by result actionable. A user can understand an occurrence from one line, open its source note, and reveal the exact citekey or wikilink without receiving a false selection when the source has changed.

Acceptance criteria

• Each expanded source group shows one line of context for every Citation Occurrence.
• The exact citekey or wikilink token is emphasized within the context.
• Context is read only for expanded groups and cached by note path and modification time.
• A note change invalidates its cached context.
• An unreadable context keeps the source group and shows: Preview unavailable.
• Selecting a source heading opens the citing note.
• Selecting an occurrence opens the source note and reveals its exact range when the range still matches.
• Normal Obsidian modifier behavior can open the source in another leaf.
• A stale source position opens the note without applying an incorrect selection.
• Rendered sidebar tests cover lazy reads, caching, invalidation, unavailable previews, exact-token emphasis, opening, modifier behavior, exact navigation, and stale fallback.

Blocked by

• Ticket 1: Show literal citations in the Cited By Sidebar.

[aidenlx]

Completed in commit 921098f0.

Delivered lazy one-line context previews, exact-token emphasis, path-and-mtime caching, preview failure handling, source opening, exact-range navigation, modifier behavior, and stale-range fallback with rendered-view tests.