[owjs3901]

Summary

The audit flagged a decision (b) regression. Since #736 (70dac33), every styled component the file exports has an a--N marker class. In extractor__tests__emotion_component_selectors.snap, Parent has one even though no selector names it, while #730 had limited markers to components a selector references.

This PR leaves the behavior as it is and explains why. Removing these markers would break selectors that work today:

• markers_of(name, exported, selected) gives an exported component one marker per export name, css::component_marker(export, index, filename). A module that imports it computes that same marker from the export when it selects the component (${Child} { ... }, [Child]) or extends it (styled(Child)). The imported_components_are_selected_by_the_class_their_module_gives snapshots cover this.
• Each file is built on its own. The defining module never learns which modules import it, and in dev or incremental builds it is often compiled before or without them.
• Only the element the component renders can carry the class. The importing module can write the selector, but it cannot add a class to elements that another module renders. Atomic style classes are shared between components, so they cannot stand in as the marker.

So a marker on an exported component can't wait until something references it. Components a file keeps to itself still get a marker only when a selector in the file names it, which is #730's behavior. The other marked class in that snapshot, Wide, carries Child's marker because it extends Child. That is Emotion's semantics, not an extra marker.

Changes:

• Doc comment on markers_of recording the reason.
• limitations page: a "Known limitations" entry describing the marker on exported components.

Refs #690

Test plan

• cargo fmt --all -- --check (comment and docs only; no code path changes)
• CI

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
libs/extractor/src/visit.rs	100.00% <100.00%> (ø)

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