Expose production marker-text helper to native CSS contracts #797

Parent CSS epic: #235
CI owner: #227

Problem

The Native Linux document contracts workflow fails to compile tests/NativeWeb/css_service.cpp after the details-marker suppression work. The test calls webscene_native::list_marker_text(...), but the production helper is defined in the native DOM translation unit's anonymous namespace and is absent from the public native DOM declaration surface.

Failing run: https://github.com/SceneTech/WebScene/actions/runs/35489700980

Fix

• give the existing production helper ordinary webscene_native linkage and declare it beside the native DOM API;
• keep its implementation and all marker semantics unchanged;
• avoid duplicating marker-text rules in the CSS service contract.

Acceptance

• native document-contract target compiles (focused rerun pending);
• focused details-marker CSS contract uses the production helper;
• no DOM/style/layout/paint behavior changes.

Merged result — 20 September 2026

PR #798 is merged at WebScene c9a28121e5df848d2d41a00ed09dc42857ed5e67. Source and link-target review confirms the existing implementation is unchanged; the focused native contract rerun remains the compile acceptance authority.