Enhance community detail graph UX

[forhappy]

Summary

• group community-detail nodes into semantic color-and-shape families for callables, types, modules/files, boundaries/data, and fallback nodes
• color edges by execution, dependency, structure, or data/event-flow purpose while preserving confidence dash and width cues
• add an accessible, theme-aware legend and mirror semantic colors in the minimap
• rebuild the shared embedded viewer assets so exported HTML and the VS Code extension use the same presentation

Compatibility

No CLI, graph schema, or transport contract changes. Existing exported HTML remains self-contained and must be regenerated with an updated Compass build to receive the new viewer assets.

Verification

• npm run typecheck:js
• npm run test:js (203 viewer unit tests, 120 VS Code tests, 83 Chromium tests)
• node scripts/check_viewer_assets.mjs
• git diff --check