perf(ActionList): enable React Compiler

[hectahertz]

Summary

Enable React Compiler for ActionList — the foundational component used by ActionMenu, SelectPanel, NavList, and FilteredActionList.

ActionList was originally excluded from the compiler during the initial migration. After analysis (build, lint with eslint-plugin-react-compiler, and manual Storybook verification), all ActionList source files are fully compiler-compatible. The only fix needed was a Rules of Hooks violation in a story file.

Changes

• Remove src/ActionList/**/*.tsx from the React Compiler unsupported list in react-compiler.mjs
• Fix a nested component definition in ChildWithSideEffects story — moved SideEffectDescription to module scope to comply with the Rules of Hooks

Why this matters

ActionList is the most-rendered list component in the design system. With the compiler enabled, React will automatically memoize ActionList's components (Item, List, Group, Selection, Visuals, etc.), reducing unnecessary re-renders without any manual React.memo / useMemo / useCallback work.

How did you test this change?

1. Lint — Ran npx eslint with react-compiler/react-compiler rule on all ActionList files (source, stories, tests): 0 warnings

2. Build — npx turbo build --filter=@primer/react --force passes cleanly with ActionList compiled

3. Storybook — Verified the following stories render correctly with zero console warnings:

   • ActionList Default
   • ActionList Single Select (with click interactions)
   • ActionList Multi Select (with click interactions)
   • ActionList With Avatars
   • ActionMenu with 100 items (overlay open)
   • SelectPanel default (overlay open, filter interaction)
   • NavList default

[changeset-bot]

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Latest commit: f2fe7ee

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[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Or, apply the integration-tests: skipped manually label to skip these checks.