[WKJBryan]

Summary

• Make dense maps legible with semantic zoom: hub labels and structural links at overview, note labels and ordinary links as detail increases, focused and searched notes remain discoverable.
• Add bounded layout spacing by existing relationship kind; no claim that structural distance is a calibrated semantic score.
• Add an explicit append-only perspective history with source note validation, effective and recorded times, and a backward lineage in the graph Time panel.
• Document the later stages for semantic proximity, stable historical slices, and a side-on time view.

Verification

• Frontend: 435 tests passed; production build passed; targeted ESLint reported no errors.
• Rust unit tests were added for the ledger but could not be run locally because this environment lacks Cargo. CI Rust checks must pass before merge.

Scope

The Time panel overlays recorded perspective states on the current graph. It does not reconstruct historical note layouts or infer earlier beliefs from timestamps. SVG element counts and simulation cost are unchanged.

Addresses #108.