feat(editor): add snap enable toggle

[ChrisBeWithYou]

Summary

• split snap on/off into a dedicated toolbar toggle instead of using Off as a snap resolution
• preserve the selected snap resolution when snap is disabled
• wire FeedBack Native G to toggle snapping
• update snap option and shortcut tests for the separated snap state

Testing

• node --check screen.js
• node tests/snap_options.test.js
• node tests/eof_shortcuts.test.js
• all tests/*.test.js via node

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b28e5ce2-6f11-477b-a419-1f5d98c5c224

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/editor-snap-toggle

---

_{Comment @coderabbitai help to get the list of available commands.}

[byrongamatos]

Review pass (Claude Code) — stacked on #57. Own snap-toggle logic is correct: snapEnabled (default true) + _editorEffectiveSnapValuePure(enabled, value) → enabled ? value : 0, editorSetSnap now clamps + syncs the select, editorSetSnapEnabled syncs the checkbox. node --check + all JS tests green.

Two things to fix before this lands:

1. [bug — inherited] Drum-edit G/F shadowed. This stack is based on the pre-fix feat(editor): wire FeedBack Native hotkeys #55: the drum g/f/k articulation handler (screen.js:3886) is still after the shortcut dispatch (3773), and this PR adds FeedBack-Native G → toggleSnap. So in drum-edit mode G toggles snap (and F edits fret) instead of setting ghost/flam. I already fixed exactly this on feat(editor): wire FeedBack Native hotkeys #55's branch (moved the drum g/f/k handler before the dispatch — it covers g/f/k, so G→toggleSnap is correctly shadowed by ghost in drum mode). Rebase feat(editor): add shortcut interaction settings #56–feat(editor): add tempo signature denominator control #61 onto the updated feat(editor): wire FeedBack Native hotkeys #55 and it resolves cleanly; I didn't apply a duplicate here because it would conflict on that rebase.
2. [conflict] Snap model vs editor: upgrade snap grid and timeline jumps #46 + feat(editor): expand snap grid options #57. With feat(editor): expand snap grid options #57 this converges toward editor: upgrade snap grid and timeline jumps #46's snapEnabled model but is still a separate SNAP_OPTIONS definition — same editor: upgrade snap grid and timeline jumps #46 overlap flagged on feat(editor): expand snap grid options #57. (Codex second-opinion rate-limited until ~1 AM — manual + test-backed.)