Carry source button height constraints through native wrappers

[chubes4]

Scope

Preserve source height constraints and selector specificity across core/buttons, core/button, and the rendered link. Includes variable-backed CSS math, minimum-height inheritance, responsive auto resets, and mixed-selector geometry projection without discarding non-button source rules.

Verified

• Full composer test suite passes, including 305 parity fixtures and package-install proof.
• Browser regression covers a higher-specificity layout rule preceding a shared lower-specificity skin rule.
• Fresh Studio URL import of https://www.busybearscleaning.com/ with candidate 3e1c49d confirms exact CTA geometry: mobile 161.109375 x 45.859375px, desktop 183.453125 x 52.203125px; corner radii also match.
• All four routes load without browser errors or horizontal overflow at 390/1440; every editor block is valid.

Evidence And Remaining Gates

The earlier desktop failure is resolved: wrapper projection was erasing source specificity, allowing a later 10px minimum-height skin rule to win. The fix uses the existing specificity-preservation machinery rather than an arbitrary priority increase.

This remains draft pending review and CI. Whole-site parity is not claimed: form label-marker typography and row spacing still differ. The paired import included #1647 and Automattic/static-site-importer#1579; this PR isolates button-height work.

Reproduce

From php-transformer run composer test. From php-transformer/tools/visual-parity run npm ci and npm test with Playwright Chromium available. For full-site verification, package this candidate with the paired form work into an SSI development ZIP and use Studio PR #3952 create --from https://www.busybearscleaning.com/ --keep-source --static-site-importer-path <zip>.

AI assistance: OpenAI gpt-6-astra via OpenCode orchestrated diagnosis, corrected specificity projection, reviewed changes, and performed fresh Studio/browser verification. OpenAI gpt-5.6-terra via OpenCode implemented and tested the earlier isolated compiler candidates.