feat(vscode): improve query and call graph input UX

[forhappy]

Summary

• add a persistent top accent and stronger selected state for the active Ask, Explain, or CompassQL mode
• source query autocomplete exclusively from bounded typed searches of the active Compass code graph; historical panels search their selected immutable revision with --at
• add graph-backed callable-symbol autocomplete to the Call Graph pane for functions, methods, constructors, and callable properties
• debounce graph searches, cancel stale or concurrent completion processes, reject invalid or oversized responses, and preserve manual query/call tracing when suggestions fail
• support Unicode graph terms, ranked and deduplicated suggestions, Arrow/Tab keyboard navigation, Enter execution, responsive layouts, and high-contrast status states
• make Explain accept the highlighted completion on Enter and submit its exact graph node ID behind the readable qualified name
• make compass explain resolve unique exact qualified names end to end, including through the compact traversal cache, while preserving ambiguity for duplicates

Verification

• npm run typecheck:js
• npm run test -w @compass/viewer (210 passed)
• npm run test -w editors/vscode (143 passed)
• npm run test -w @compass/viewer-tests -- query.spec.ts (12 passed)
• full browser suite: 85/87 passed in parallel; the two unrelated graph-canvas double-click timing checks both passed in a serial rerun
• cargo test -p compass-model --lib --locked (26 passed)
• cargo test -p compass-query --lib --locked (159 passed)
• cargo test -p compass-cli --test code_query_cli explain_ --locked (3 passed)
• cargo test -p compass-cli --test help_cli --locked (5 passed)
• cargo clippy -p compass-model -p compass-query -p compass-cli --all-targets --all-features --locked -- -D warnings
• replayed compass explain against the Colima graph for cmd/daemon.start and cmd/daemon.pinger::Start
• node scripts/check_viewer_assets.mjs
• npm run build -w editors/vscode
• npm run package -w editors/vscode
• npm run smoke:vsix -w editors/vscode