Build SVG/HTML lettering editor foundation

[realproject7]

Parent: #197

Proposal reference: ~/z-docs/PROPOSAL-plotlink-ows-webtoon-pivot.md

Context

Manual lettering is MVP-required. The editor surface should use SVG/HTML overlays for selectable, draggable, resizable bubbles and text.

Scope

• Add the base cartoon lettering editor for one selected cut.
• Render clean image as the background.
• Render overlay objects in normalized coordinates.
• Support selecting overlays and showing basic inspector state.
• Persist no advanced tools yet beyond a minimal editable overlay model.

Acceptance Criteria

• Editor opens for cartoon cuts only.
• Overlay coordinates scale correctly with preview size.
• Selection state works without affecting terminal or fiction editor behavior.
• Tests cover coordinate normalization and editor rendering.

Public Safety

This is a public repo. Do not include secrets, API keys, wallet private keys, mnemonics, auth tokens, OWS vault internals, private story drafts, or sensitive local paths in issues, PRs, logs, docs, tests, or examples.