[ellenbauer]

Refs #2726

What was wrong

With #2719 and #2720, the Dunbar Oaks (Wix) phone menu opens, but the panel is white instead of the source's beige and its column sits about 14px right of the source. Both come from the projected dialog's own box, not from the navigation.

The menu panel #MENU_AS_CONTAINER is held twice in the compiled page. The capture's hidden wired copy (#dla-dialog-0 > #MENU_AS_CONTAINER) keeps the panel's id. The captured open state becomes the native <dialog> under a generated id (blocks-engine-dialog-<hash>), because the id is already taken. Two things follow:

1. Id rules miss the dialog. Wix places and paints the panel through id rules: #MENU_AS_CONTAINER{left:calc(50% - 160px);width:320px;--bg-overlay-color:rgb(var(--color_32))}. The background layer inside paints with .LNYVZi{background-color:var(--bg-overlay-color)}. Class rules on the panel already reach the dialog (the projector binds both elements), but these id rules reach only the hidden copy. The dialog had no offset and no paint variable.
2. The dialog keeps the user agent box. The source panel is a div, so it never had the user agent's dialog box: 1em padding, a 3px solid border, Canvas (white) paint, auto margins, insets and size caps. On the dialog these pushed the content 13px in and drew a white, black-framed box. The block stylesheet already resets that box for in-place dropdowns, but not for modals.

What changed

• CapturedDialogProjector: when another element still holds the captured root's id, the dialog carries it as its editor anchor class (blocks-engine-editor-anchor-MENU_AS_CONTAINER). The capture's own panel envelope (data-blocks-engine-capture-dialog-panel) does not count, because its id is the wiring key.
• ScopedAnchorSelectorProjection::identities(): an id that a source element carries as its editor anchor class is projected as :is(#id,.blocks-engine-editor-anchor-id). This is the mechanism already used to keep id selectors live across document variant id suffixes. The specificity shims are unchanged, so the rule keeps its source weight.
• CapturedDialogConverter: a modal whose own author rules position it (position:fixed or absolute) gets placement: "source". The cascade is resolved through the compilation's StyleResolver.
• CapturedDialogBlockGenerator: :where(dialog:not([data-blocks-engine-presentation])[data-blocks-engine-placement="source"]) resets inset, size caps, margin, padding, border, background and color. It has zero specificity, so every source rule still wins. Modals that do not position themselves keep the user agent box, which is their only placement.

These are two causes in one PR because neither alone puts the column where the source has it: the offset needs both the id rule (left, width) and the box reset.

Tests

• New tests/unit/captured-dialog-source-panel-box.php, 5 assertions (projector, compiled CSS, block placement, stylesheet). On trunk, 4 fail; all pass here.
• capture-evidence-equivalence: the 12 native dialog cases are re-recorded and noted in its README. Only the emitted style.css text and the hashes derived from it change (7a7af898 also gains one style-rule cache hit). Checked by replaying each case on trunk and on this branch and diffing the normalized output.

End to end

Studio imports of the Dunbar Oaks capture with v0.38.1 (the last base that reads these captures), iPhone user agent at 375. Quality gate passed on both.

• Base (localhost:8914): dialog at x=29, 346 wide, 10px padding, 3px border, white.
• With fix(php-transformer): stack declared block menu items in core flow layout #2742, fix(php-transformer): keep wrapped peer menu items flat and off panel classes #2743 and fix(php-transformer): keep the source panel box on a projected modal dialog #2744 (localhost:8940): dialog at x=27.5, 320 wide, no padding or border, the background layer paints rgb(233, 220, 211) as in the source.
• 1280 and 375 closed: 0 differing pixels between the two imports.
• St Francis (localhost:8941): the panel keeps the Canvas backdrop (its own background layer does not paint in the import), so it stays white rather than transparent.
• composer test (memory_limit -1) passed.

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