fix(php-transformer): ignore inert live-region scaffolding

[chubes4]

Closes #1548

Supersedes #1552, which GitHub closed when its branch was renamed to remove platform-specific scope.

Summary

• classify empty custom-element live-region scaffolding exclusively from observable DOM semantics
• require an attribute-free custom wrapper with one empty, bounded, visually clipped ARIA live region
• omit qualifying runtime scaffolding instead of generating empty HTML fallbacks
• preserve wrappers with captured text, semantic names, unexpected attributes, runtime metadata, or unrelated custom-element structure
• keep the observed platform wrapper only as regression input proving wrapper-name independence

Verification

• php tests/unit/inert-capture-scaffolding.php (21 assertions)
• composer test on current trunk after fix(php-transformer): chunk oversized projected stylesheets #1550, fix(php-transformer): preserve responsive button layouts #1551, and feat(php-transformer): generate canonical theme toggles #1553 (297 parity fixtures plus package-install proof)
• production-shaped 102-page import: removed 204 empty live-region fallbacks while retaining zero content-loss findings
• production source contains no platform or wrapper-name condition
• git diff --check origin/trunk...HEAD

AI assistance

OpenAI GPT-5.6 Sol via OpenCode inspected repeated fallback evidence, replaced the initial platform-specific condition with a bounded semantic classifier, added wrapper-independent and fail-closed tests, and reran the focused and full verification on the merged upstream state under Chris Huber's direction.