Implements Task 10 of the terminal file viewer plan: highlightLine.ts
(line-range StateField + setHighlight effect), viewerTheme.ts (EditorView
theme + syntax HighlightStyle), and CodeEditor.tsx (the React wrapper with
getDoc/setDoc/goTo/focus).
Also implements languages.ts + languages.test.ts, moved here from Task 7
per preflight ruling P1 (they need @codemirror/* packages, which only
Task 6 installs).
Preflight rulings applied:
- P1: languages.ts/.test.ts live here, not in Task 7.
- P12: syntax colours are `--syntax-*` custom properties in index.css,
not hard-coded hex.
- P13: languageFor tests assert `.not.toBeNull()` for mapped extensions
and move README to the "returns null" case, instead of the vacuous
`.resolves.toBeDefined()`.
- P14(c): readOnly extension array factored into readOnlyExt(readOnly)
instead of being duplicated in CodeEditor.
- P16: no custom Mod-g binding; searchKeymap's Mod-Alt-g covers "go to
line" already.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
shadowdaoandClaude Opus 5.5
5b66e861df