Migrate interactive roots to mergeProps

[joshblack]

Part of the ADR-025 prop merging migration.

This PR updates a group of lower-volume selection and interactive-data components to merge component-authored and consumer-authored props through mergeProps. The changes preserve existing refs, event ordering, consumer precedence, class names, and accessibility behavior while removing 43 findings from the migration report.

Changelog

New

• Add stricter Checkbox coverage to confirm consumer handlers run once per interaction.

Changed

• Update Autocomplete, Checkbox, DataTable, Details, FilteredActionList, Overlay, Pagination, Popover, ProgressBar, ScrollableRegion, Select, SelectPanel, Timeline, and ToggleSwitch roots to use the ADR-025 prop-merging convention.
• Preserve explicit consumer undefined precedence for Autocomplete overlay focus behavior.
• Preserve consumer polymorphic overrides for SelectPanel secondary links.

Removed

• None.

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

This is a behavior-preserving migration and does not change the public API, so no changeset is required.

Testing & Reviewing

• Review event ordering and cancellation for Autocomplete, Checkbox, Overlay, and SelectPanel.
• Review controlled attributes and consumer precedence across the migrated roots.
• Confirm the mergeProps migration report decreases from 144 findings across 66 files to 101 findings across 48 files.
• Targeted component tests and the @primer/react type-check pass.

[changeset-bot]

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Latest commit: 0fe27ce

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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.