F14.2d — Keep guided canvas coordinates and numbering aligned

[Flow-Fly]

Parent: #130. Depends on completed F14.1 / #129.

Guard normal UI paths that would invalidate the durable guide map while preserving creative drawing and navigation.

Acceptance:

• Guided projects cannot resize, flip, or rotate the canvas/layer through Image actions.
• Reference import, palette replacement/editing, frame add/delete, layer add/delete/reorder, and visibility/lock structure controls are disabled or replaced.
• Explanatory copy states why the structure is fixed.
• Pencil, eraser, arbitrary drawing colors, undo, redo, pan, zoom, touch pinch, zoom-to-fit, export, rename, duplicate, and optional CRT remain available.
• Normal projects retain existing behavior.

[Flow-Fly]

Completed in PR #315. The implementation is merged into develop at a9ed5f9 and post-merge CI run 29086892806 passed.