fix(php-transformer): preserve responsive button layouts

[chubes4]

Closes #1186

Summary

• carry responsive width declarations through native core/buttons and core/button wrapper topology
• preserve authored flex alignment, gap, and breakpoint padding over WordPress button defaults
• avoid unconditional full-width wrapper bridges when a later breakpoint restores intrinsic width
• retain nested icon/label content and valid Gutenberg serialization

Verification

• php tests/unit/button-signal-classifier.php
• php tests/unit/engine-support-css-asset.php (66 assertions)
• php tests/contract/run.php
• php tests/parity/run.php (292 fixtures)
• composer test
• production-shaped import: desktop Sign Up control retained display:flex, gap:8px, padding:8px 16px, and 44px height
• git diff --check origin/trunk...HEAD

AI assistance

OpenAI GPT-5.6 Sol via OpenCode traced responsive source rules through generated native button wrappers, implemented the generic projection changes, added regression coverage, and ran the focused, full, package, import, and browser verification under Chris Huber's direction.