Push margin-top of TimelineBody +1px

[llastflowers]

Closes https://github.com/github/primer/issues/6438

Changelog

Changed

Added +1px to the margin-top of TimelineBody to improve visual alignment of elements

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

Good test stories:

• https://primer.style/react/storybook/?path=/story/components-timeline-features--timeline-break
• https://primer.style/react/storybook/?path=/story/components-timeline-features--with-inline-links

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: c5f8f55

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

This PR includes changesets to release 0 packages

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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. Or, apply the integration-tests: skipped manually label to skip these checks.

[Copilot]

Pull request overview

Adjusts the Timeline component’s visual spacing to better align TimelineBody content with surrounding Timeline elements, addressing primer issue #6438.

Changes:

• Increases TimelineBody top margin by 1px via calc() to improve vertical alignment.
• Adds a targeted stylelint disable for the spacing rule on the updated declaration.

[HiroAgustin]

Adding the 1px calc feels icky to me, try with.

Suggested change

	margin-top: calc(var(--base-size-4) + 1px);
	margin-top: 0.25lh;

[llastflowers]

We generally avoid using lh (and don't currently have any uses in our repo) because of Safari compatibility issues. We'd have to suppress the lint warning and provide a fallback value to cover unsupported browsers, which ends up being less clean overall. This calc() pattern is what we usually use when we need an in-between value not directly provided by our existing CSS variables, so I lean toward keeping things consistent.

[HiroAgustin]

@copilot add patch changeset

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/14686

[primer-integration]

Integration test results from github/github-ui:

  CI Passed
  VRT Running
  Projects Passed

[llastflowers]

integration tests passing but VRT status is not reporting here. Added skip label to unblock this PR