Summary

• add temporary Hide numbers and Preview target controls that never write pixels or history
• add an immediately visible Finish guidance action with explicit confirmation at any coverage
• persist finishing safely: the guide payload is omitted only for the confirmed save, with automatic restoration and an error if saving fails
• preserve artwork, undo/redo history, CRT state, and normal editor tools when guidance ends
• add Guided Drawing beside normal creation in Project Library while retaining the secondary File menu entry
• restore index-only cel data robustly and prove a mid-session project resumes its target, settings, view defaults, palette numbering, and painted coverage

Product behavior

The artist decides when the scaffold has done its job. Preview is temporary, finishing never auto-fills or auto-triggers, and completing guidance simply returns the same artwork to the normal editor at a useful fitted view.

Issues

Closes #316
Closes #317
Closes #318

Part of #131 and #128.

Verification

• npm run test:run — 484 tests passed
• npm run lint -- --quiet
• npm run build
• npx fallow audit --changed-since origin/develop — no issues
• git diff --check
• live browser pass on a 1280x720 viewport, including immediately visible view controls and Finish guidance

The production build retains the existing dynamic-import and large-chunk warnings.