chore: graduate primer_react_overlay_max_height_clamp_to_viewport

[francinelucca]

This pull request removes the feature flag controlling the "max-height clamp to viewport" behavior for overlays and action menus, making the viewport-clamped max-height the default. Now, all overlays and action menus will have their max-height restricted to the viewport without needing a feature flag.

Max-height size token rules use min(Xpx, 100vh) as the default fallback for browsers that don't support dynamic viewport units, and progressively enhance to min(Xpx, 100dvh) via @supports (height: 100dvh) in supporting browsers.

Changelog

New

Changed

• Max-height size token rules in Overlay.module.css and ActionMenu.module.css now use min(Xpx, 100vh) as a fallback, with @supports (height: 100dvh) overriding to min(Xpx, 100dvh) for browsers that support dynamic viewport units

Removed

• primer_react_overlay_max_height_clamp_to_viewport FF and associated code

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

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: b90c0ce

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	Minor

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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.

[Copilot]

Pull request overview

Removes the primer_react_overlay_max_height_clamp_to_viewport feature flag and makes viewport-clamped max-height behavior the default for Overlay and ActionMenu.

Changes:

• Removes the feature-flag gating and related data-max-height-clamp-to-viewport attribute usage in Overlay and ActionMenu.
• Updates CSS so max-height size tokens use min(<token>, 100dvh) by default.
• Deletes the flag from DefaultFeatureFlags.

Show a summary per file

File	Description
packages/react/src/Overlay/Overlay.tsx	Removes feature-flag logic and stops conditionally adding the clamp data attribute
packages/react/src/Overlay/Overlay.module.css	Makes viewport clamping the default for max-height size tokens
packages/react/src/FeatureFlags/DefaultFeatureFlags.ts	Removes the graduated feature flag from defaults
packages/react/src/ActionMenu/ActionMenu.tsx	Removes feature-flag logic and stops conditionally adding the clamp data attribute
packages/react/src/ActionMenu/ActionMenu.module.css	Makes viewport clamping the default for max-height size tokens

Copilot's findings

• Files reviewed: 6/6 changed files
• Comments generated: 3

[primer]

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

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/18054

[primer-integration]

Integration test results from github/github-ui:

  CI Failed
  VRT Failed
  Projects Passed

CI check runs linting, type checking, and unit tests. Check the workflow logs for specific failures.

VRT check ensures that when visual differences are detected, the PR cannot proceed until someone acknowledges the changes by adding the "visual difference acknowledged" label.

Need help? If you believe this failure is unrelated to your changes, please reach out to the Primer team for assistance.