feat: add size option for Tag Buttons

[Bracciata]

Closes #1957

Summary

• Adds a size prop ('default' | 'small') to Button (when variant="tag") and TagButton
• Exports a shared TagSize type from the Tag component
• Refactors ButtonProps into discriminated union types so size is only valid when variant="tag" (type error otherwise)
• Adds screenshot tests for the small tag variant for both Button and TagButton
• Adds documentation and examples for the new size prop in both Button.mdx and TagButton.mdx
• Fixes autoprefixer converting :user-invalid to :invalid in select.css, which caused required selects to show error styling before user interaction
• Fixes TextEllipsis[hideTooltip][maxLines=2] test to actually hover and assert no tooltip appears
• Removes unnecessary dark mode screenshots for TextEllipsis[hideTooltip] tests (component has no dark mode styling)

Test plan

• Button with variant="tag" and size="small" renders with Tag--small class
• Button with non-tag variant and size prop produces a TypeScript error
• TagButton with size="small" passes the size through to the underlying Button
• Screenshot baselines match expected styling for small tag buttons
• Required Select fields show no error border before user interaction
• Required Select fields show error border after user interacts and leaves the field empty
• TextEllipsis[hideTooltip] tests hover and verify no tooltip is shown

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[Copilot]

Pull request overview

Adds support for rendering Button with variant="tag" at the smaller Tag size, aligning Button’s tag variant behavior with the existing Tag component sizing API (Issue #1957).

Changes:

• Added a size prop to Button and TagButton and applied Tag--small styling when variant="tag" and size="small".
• Added unit tests covering size="small" for both Button (tag variant) and TagButton.
• Added Playwright component screenshot coverage and committed new baseline images for small tag buttons (light/dark).

Reviewed changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/react/src/components/TagButton/index.tsx	Plumbs size through TagButton into Button.
packages/react/src/components/TagButton/index.test.tsx	Adds a unit test asserting Tag--small is applied.
packages/react/src/components/Button/index.tsx	Introduces size prop and toggles Tag--small class for tag variant.
packages/react/src/components/Button/index.test.tsx	Adds unit test for small tag button class behavior.
packages/react/src/components/Button/screenshots.e2e.tsx	Adds screenshot test for variant="tag" + size="small" states (light/dark).
e2e/screenshots/button-variant-tag-size-small-.png	New baseline screenshot (light theme).
e2e/screenshots/dark--button-variant-tag-size-small-.png	New baseline screenshot (dark theme).

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[frankensteinke]

I think we'd probably want to add this new prop to the docs for Button and TagButton. Here's what Claude told me that would involve:

• docs/pages/components/Button.mdx — add a size entry to the ComponentProps at line ~119 (noting it's only valid when variant="tag"), and optionally a new example under the Tag section (~line 81) showing <Button variant="tag" size="small">Small Tag</Button>.
• docs/pages/components/TagButton.mdx — add a size entry to the ComponentProps array at line 30, and optionally an example alongside the one at line 15.

Both use the shared <ComponentProps> component, so it's just an object append like:

{
  name: 'size',
  type: ['default', 'small'],
  defaultValue: 'default',
  description: '...'
}

---

Other than that, I just left some minor pieces of feedback. Thanks for contributing!

[frankensteinke]

Weird that these screenshot file names end with a hyphen, but I don't think it's related to anything in this PR.

[Bracciata]

Agreed. Maybe we open new issue?

[frankensteinke]

#2329 done!

Addressed

[frankensteinke]

Looks good! Just left some nits about other test .getByText calls that could be changed to .getByRole.

[frankensteinke]

#2329 done!

[frankensteinke]

Nit: there are some other .getByText calls that could be updated to .getByRole.

[frankensteinke]

Nit: more .getByText calls that could be updated to .getByRole.