Remove BoxWithFallback usage and sx prop from InputLabel and UnstyledTextInput

[mperrotti]

Relates to https://github.com/github/primer/issues/5424 and https://github.com/github/primer/issues/5828

Changelog

New

Changed

Removed

Removes sx prop from FormControl.Label and internal text input-related components

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 (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: fe5808f

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

This PR includes changesets to release 2 packages

Name	Type
@primer/react	Major
@primer/styled-react	Major

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[Copilot]

Pull Request Overview

This PR removes dependencies on BoxWithFallback and the sx prop from InputLabel and UnstyledTextInput components as part of the migration away from styled-system. The changes simplify these internal components by using native elements directly instead of the abstraction layer.

• Removes SxProp and sx parameter support from both components
• Replaces BoxWithFallback usage with direct native element rendering
• Updates type definitions to use modern polymorphic patterns for InputLabel

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/react/src/internal/components/UnstyledTextInput.tsx	Removes SxProp import and BoxWithFallback usage, returns native input element directly
packages/react/src/internal/components/InputLabel.tsx	Removes SxProp and BoxWithFallback, implements modern polymorphic typing and direct element rendering

[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/3919

[primer-integration]

🟢 ci completed with status success.

[github-actions]

👋 Hi, there are new commits since the last successful integration test. We recommend running the integration workflow once more, unless you are sure the new changes do not affect github/github. Thanks!

[github-actions]

👋 Hi, there are new commits since the last successful integration test. We recommend running the integration workflow once more, unless you are sure the new changes do not affect github/github. Thanks!