Preserve visible labels and editable native blocks in imported HTML controls

Imported pages can retain visible control text and semantic headings while generated markup lacks native Gutenberg editability or visible label presentation.

Track a generic compiler/materializer fix with regression coverage; preserve CSS ownership and avoid source-specific selectors.

AI assistance: OpenCode using openai/gpt-5.6-terra investigated the imported artifact and opened this tracker.

Start by tracing the generic compiler/materializer path that handles the imported artifact; the issue names no specific files or entry points. Add regression coverage showing that visible labels and semantic headings remain present, generated controls remain natively editable in Gutenberg, CSS ownership is preserved, and the fix does not depend on source-specific selectors.

Written by the indexing model from the issue text.