Keep author-layout asset rewrites editor-valid

[chubes4]

Problem

The integrated Weebly parity candidate rewrites local asset URLs in saved blocks-engine/author-layout markup, but the block attribute still serializes the original relative content. Gutenberg compares the save output against persisted markup and reports five invalid blocks. The same fixture was fully editor-valid before the new bounded visual/image projection changes.

Acceptance

• Asset publication/rewrite keeps blocks-engine/author-layout attributes and saved markup semantically identical.
• Local SVG and bounded visual assets render from published theme URLs.
• The four-surface Weebly fixture returns to 100% editor validity.
• Add deterministic contract coverage for relative-to-published asset rewriting inside author-layout content.

Evidence

/var/folders/lr/c_cmmt7s0592m4njz99v5yb40000gn/T/opencode/weebly-four-surface-direct-r59/summary.json records five editor_block_invalid findings where relative website/assets/materialized-svg/*.svg attribute content differs from runtime-rewritten theme URLs.

AI assistance

OpenAI gpt-5.6-sol through OpenCode analyzed r59 evidence and drafted this issue. Chris Huber remains responsible for scope and implementation decisions.