Fix FilteredActionList skeleton SSR widths

[joshblack]

Changelog

New

N/A

Changed

• FilteredActionList body skeleton rows now use deterministic CSS-module widths instead of render-time randomness, making the loading state SSR-compatible.

Removed

• Removed the redundant FilteredActionListBodyLoader test asserting that Math.random is not called.

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

Testing & Reviewing

• npx vitest run packages/react/src/FilteredActionList/FilteredActionList.test.tsx
• npm run format:diff
• npm run lint
• npm run lint:css
• npm run type-check
• npm run build
• npm test -- --run
• Storybook started successfully and responded for /?path=/story/components-filteredactionlist--default

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github-ui (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 9640da4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

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[github-actions]

⚠️ Action required

👋 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. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

To publish a canary release for integration testing, apply the Canary Release label to this PR.

[primer]

🤖 Lint and formatting issues have been automatically fixed and committed to this PR.