Convert canonical standalone search controls to native blocks

[chubes4]

Summary

• convert strict, script-free, single-input search controls using the canonical WordPress query name s to dynamic core/search blocks
• preserve arbitrary HTML search controls, ID-addressable controls, runtime targets, and wrappers with additional descendants on existing preservation paths
• restore the package boundary: php-transformer contains no active Figma-specific source, test, tool, or documentation knowledge
• move the Figma acceptance contract to repository scope and make figma-transformer supply its DOM identity attributes explicitly
• add dedicated CI for the Figma owner and generic visual-parity tools

Addresses #619.

Architecture

figma-transformer
  owns .fig semantics and Figma DOM identity attributes
          |
          | generic HTML + explicit provider configuration
          v
php-transformer
  owns format-neutral HTML -> blocks and generic visual probes

Historical generated CHANGELOG.md entries are unchanged per repository policy.

How to test

1. Run cd php-transformer && composer install --no-interaction --prefer-dist && composer validate --strict && composer test.
2. From the repository root, run php tests/contract/production-acceptance-matrix.php.
3. Run cd figma-transformer && composer install --no-interaction --prefer-dist && composer validate --strict && composer test.
4. Run cd php-transformer/tools/visual-parity && npm ci && npm test.
5. Confirm the PHP Transformer package contains no active Figma references with grep -RniE "figma|data-figma" php-transformer/src php-transformer/tests php-transformer/tools.

Behavior and compatibility

• Native conversion is based only on generic HTML semantics: one script-free search input, no ID, canonical query name s, and no additional descendants.
• Arbitrary search forms and runtime-addressable controls retain existing preservation behavior.
• The generic DOM provider defaults change from product-specific attributes to data-node-id and data-node-name; callers with other emitter contracts now configure those attributes explicitly.
• figma-transformer preserves its existing DOM-box behavior by supplying its own attribute contract.
• No public PHP APIs or extension paths change.

Evidence

• Full PHP Transformer suite passes, including 244 parity fixtures and package install proof.
• Repository production acceptance contract passes from its new owning scope.
• Figma Transformer contract passes and now verifies explicit DOM identity configuration.
• Generic visual-parity smoke and browser geometry suites pass.
• Real FSE import through the generic boundary passes with native conversion rate 1.0, generated core/html count 0, and 141/141 editor-valid blocks.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode with openai/gpt-5.6-sol
• Used for: Root-cause analysis, architecture correction, implementation, regression tests, and verification under Chris Huber direction.