Size synthetic full-bleed image figures to their authored container

[chubes4]

Measured failure

The Lake Country Players About hero has a source .section-background image that fills its 1600px container (1600×~594) at 1600px viewport and 1728px container at 1728. A fresh DLA 0.6.13 → BE/SSI → WordPress import retains an editable core/image in a figure.blocks-engine-synthetic-image-figure under a full-width section-background, but the figure and image compute to 1521×594 at 1600px and 1586×619 at 1728px. The parent is correctly 1600/1728 wide. At 390px the figure is 1614px wide inside a 390px parent, clipped by overflow hidden. The synthetic figure inherited aspect-ratio:1440/562 and sizes its width from its height instead of filling the source-authored container.

Counterfactual

Read-only browser CSS .section-background figure.blocks-engine-synthetic-image-figure{width:100%} changes imported figure/image widths 1521→1600, 1586→1728, and 1614→390 at 1600/1728/390 respectively, while their heights and document height remain unchanged. Investigate generic generated background-image figure ownership; carry the source image’s fill-width contract onto the editable figure, without applying a global rule to unrelated images. Add neutral source-derived regression and verify editor serialization + real frontend.

Evidence

Source→capture sampled DLA 0.6.13 check passed all 12. Latest site import ece213bbddfb0e25f65bbcf94455f5772f9a5445109cf914637faafe5c26cdfb materialized 25/25 receipts and 27 content items, and #2338 fixed the About four-column portrait grid. Sampled source→WordPress desktop checks remain red for this image width, ~31 extra text chars and one s.w.org request. One Jetpack-gated audition form fallback independently keeps the quality gate red. Screenshot differences in retained ~/Studio/lakecountryplayers-parity-v1/www.lakecountryplayers.org/compare/about/1600 and /1728.

AI assistance

GPT-6 Sol (OpenAI) via OpenCode traced source and generated figure DOM/computed styles at three widths and tested the reversible browser counterfactual. Chris Huber directs acceptance.

[chubes4]

Ownership correction before landing: first Homeboy Cook cook-detached-87ad3076-8cee-4d74-8a98-1a5bd316c857 produced a TypeScript packages/blocks-engine/src/theme/preserve-dom candidate. The measured WordPress 7.1.2 import is packaged with the PHP transformer by SSI build:dev-package --blocks-engine-path; its saved banner is native core/image with figure.blocks-engine-synthetic-image-figure, and the owning PHP code is php-transformer/src/HtmlToBlocks/Style/SourceBlockAttributeProjector.php (synthetic class) plus PHP BlockFactory/HtmlCompilation image lowering. The TS preserve-DOM candidate is not evidence for this WordPress path and must not be merged as resolution of this issue. Reproduce against PHP block markup and its frontend CSS with a paired SSI import; source widths 1600/1728/390. AI disclosure: GPT-6 Sol (OpenAI) via OpenCode reviewed the Homeboy patch against package provenance and corrected the tracker. Chris Huber directs acceptance.