Implement shared-renderer viewport, semantic selection, and map tools

[zoeyrose]

Outcome

Use the exact released renderer for authoring previews and build editing tools over semantic IDs rather than a second pixel scanner/render implementation.

Scope and invariants

• Adapt lossless document/catalog state to bounded SceneSnapshot with explicit source spans, stable edit identities, resources, surfaces, roles, and revisions.
• Support pan/zoom, level/layer/role toggles, grid/debug views, semantic ID/depth/coverage picking, hover/selection, conservative object bounds, and linked-map context.
• Implement paint, erase, eyedropper, select/move, rectangle, bounded fill, direction/transform, copy/cut/paste, and inventory/object placement through Implement command transactions, undo/redo, and minimal atomic saves #4 commands.
• Keep renderer selection output read-only; editor resolves picked IDs back to documents and validates edit permissions.
• Update only affected scene/resources after commands and external changes.

Acceptance criteria

• Viewport RGBA and semantic masks match atrinik-render for the same scene/profile/resources.
• Selection handles overlap, tall/multipart sprites, transparency, hidden/locked roles, cross-depth scenes, and missing resources deterministically.
• Tool property/fault tests cover bounds, huge fills, stale selection, clipboard schema/version, undo/redo, and failed multi-file writes.
• No alternate projection, painter order, GPU cache, or content parser exists in editor.
• Representative map edit previews/saves/reopens exactly and passes compiler/server validation.

Dependencies and parallelization

Depends on renderer baseline/testkit, toolkit documents/catalog, and #4. Tools can be divided by command type after common selection/transaction contracts.

Licensing

Editor code/tests are MIT. Verified original past work by an approved MIT provenance grantor may be copied, migrated, or translated under the audited file/component grant; other legacy implementation remains behavior/specification input only. Authored content/assets retain exact licenses.