chore: feature flag Overlay and ActionMenu max-height viewport clamping

[Copilot]

Gates the min(Xpx, 100dvh) max-height behavior for Overlay and ActionMenu behind a single shared feature flag.

Changelog

New

• Feature flag primer_react_overlay_max_height_clamp_to_viewport (default false) in DefaultFeatureFlags.ts — controls viewport-clamped max-height for both Overlay and ActionMenu

Changed

• Overlay.module.css: max-height size tokens revert to fixed px values; viewport-clamped variants (min(Xpx, 100dvh)) now only apply when [data-max-height-clamp-to-viewport] is present
• Overlay.tsx: reads primer_react_overlay_max_height_clamp_to_viewport and conditionally sets data-max-height-clamp-to-viewport on the overlay element
• ActionMenu.tsx: updated to use primer_react_overlay_max_height_clamp_to_viewport (same shared flag as Overlay)

Removed

• primer_react_action_menu_max_height_clamp_to_viewport feature flag — replaced by the shared primer_react_overlay_max_height_clamp_to_viewport flag

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

Enable primer_react_overlay_max_height_clamp_to_viewport via FeatureFlags and verify that both overlays and action menus with a maxHeight prop clamp correctly against the viewport on narrow screens.

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)

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[changeset-bot]

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Latest commit: 65c1434

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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.

[francinelucca]

@copilot delete primer_react_action_menu_max_height_clamp_to_viewport and use primer_react_overlay_max_height_clamp_to_viewport instead for both implementations

[Copilot]

@copilot delete primer_react_action_menu_max_height_clamp_to_viewport and use primer_react_overlay_max_height_clamp_to_viewport instead for both implementations

Done in 65c1434. Removed primer_react_action_menu_max_height_clamp_to_viewport from DefaultFeatureFlags.ts and updated ActionMenu.tsx to use primer_react_overlay_max_height_clamp_to_viewport, so a single flag now controls viewport-clamped max-height for both components.