Preserve empty runtime control buttons

[chubes4]

Summary

• preserve empty ARIA/data runtime-control buttons as core/html instead of dropping them
• keep normal visible buttons on the existing core/button path
• add contract coverage for nav-toggle-style controls used by fixture scripts

Verification

• php php-transformer/tests/contract/run.php
• Fixture probe confirmed nav-toggle and aria-expanded="false" are present in generated materialization-plan markup for 10-nonprofit.
• Matrix evidence source: runner-exec-homeboy-lab-2b7b68c5-735b-4f94-9277-e1d3e345b7f9

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: diagnosing matrix findings, implementation, contract coverage, and fixture-level verification.