fix(php-transformer): preserve direct labels on captured choices

[chubes4]

Summary

Preserve a source <label> directly preceding a linked visible combobox, hidden captured panel, and native select as one field label in the form plan. The four-sibling relationship is bounded, and explicit for, wrapping, and ARIA labels keep precedence.

Fixes #2340.

Verification

• The neutral four-sibling regression failed before the change and passes now; negative cases cover unrelated labels, unlinked panels and intervening nodes. form-adjacent-source-choice.php, the canonical HTML-to-blocks contract and the WordPress site-plan contract passed. Homeboy Cook cook-detached-0b5a75f9-cecf-4ebc-8827-d4dbb0efcdc8 passed its declared gate.
• Fresh paired full Ward Studio import (SSI provider candidate plus BE 0029570bb; run a3fd8f4b1e63c165b65a40d2d7d1b2d7d077a747e55393b04c9573f8482570e7) materialized 10 pages with quality_pass=true and zero fallback, content loss or invalid blocks. Playwright at 390, 768 and 1440px found exactly the source Contact labels Preferred Contact and Service of Interest in the editable Jetpack form; the form retains two select fields and responsive geometry.
• The paired Jetpack provider change is in draft SSI #1907; until it lands and releases, this label fix alone will not make the customer site complete. A prior paired submission verified source-backed select values, and this latest import has not yet repeated submission after the label change.

Review

Validate the bounded direct-sibling association and its context deduplication. Keep draft pending CI and merged-revision import verification; do not infer full Base44 CRM migration from the public frontend.

AI assistance: OpenAI GPT-6 Sol via OpenCode authored the change through Homeboy and reviewed source and test diffs, a fresh Studio/WordPress paired import, and Chromium label geometry. Chris Huber directs merge and customer acceptance.