fix(php-transformer): size source-filled synthetic figures to container

[chubes4]

Root cause and fix

The Lake Country Players About banner source image fills both axes of its .section-background. WordPress imports it as an editable core/image wrapped in a synthetic figure; that extra figure sizes from aspect-ratio:1440/562 and its height, shrinking the image to 1521px inside a 1600px desktop container and overflowing to 1614px inside a 390px mobile container. The PHP transformer now marks only synthetic figures whose source image has explicit 100% width and height, then gives that marker a low-specificity width:100% support rule. Source height, aspect ratio and object-fit remain intact; authored figures and fixed/one-axis images do not qualify.

Tracks #2347. This draft is not full-site visual or editor-save acceptance.

Verification

• Homeboy Cook cook-detached-b9132bb1-769c-4fb9-939c-23cbb75c9dc5, candidate attempt ...-attempt-1-c41dcb79: Homeboy promoted the PHP patch and its authoritative canonical gate passed after the gate no-progress budget was raised to 900s. A read-only local canonical run also passed after merging the latest trunk. The initial Cook gate timed out after 300s of no structured progress although the suite was still running; this was a gate budget, not a PHP assertion failure.
• PHP section-background regression covers two-axis source fill, the scoped rule, and non-qualifying images. A reversible browser CSS experiment on the previous live paired import changed the rendered About figure/image widths from 1521→1600px at viewport 1600, 1586→1728px at 1728, and 1614→390px at 390, with unchanged heights and document heights. A paired package of this commit has not yet been imported; acceptance remains pending.
• The previous Cook cook-detached-87ad3076-8cee-4d74-8a98-1a5bd316c857 produced a TypeScript preserve-DOM change in the wrong renderer. It was rejected before publication; the user-facing SSI paired package uses the PHP transformer. Homeboy recovery finalization rejected the PHP candidate after a base merge changed its recorded tree. Chris Huber explicitly authorized isolated direct finalization; commit, push, and this PR occurred outside Homeboy. Both Cook run artifacts and the rejected attempt are linked from Size synthetic full-bleed image figures to their authored container #2347.

AI assistance

GPT-6 Sol (OpenAI) via Homeboy/OpenCode authored the PHP patch. GPT-6 Sol via direct OpenCode confirmed the owning pipeline, rejected the wrong-layer patch, reviewed the candidate, verified it against current trunk, and prepared this draft. Chris Huber directs site acceptance and retains landing authority.