Timeline: CommentCard uses shared MutedTime permalink helper

[janmaarten-a11y]

Summary

Part of Phase 2 of the Timeline events work (github/primer#6663), and a follow-up to #8072 (merged). It adopts the shared permalink-time helper added in #8140.

The CommentCard internal helper had the muted, underlined permalink timestamp baked inline. This swaps it for the shared MutedTime helper called with href, which renders that exact pattern. Storybook-only, nothing ships in the package.

Changelog

New

• None.

Changed

• CommentCard now renders its permalink timestamp via the shared MutedTime helper (<MutedTime date={…} href="#" />) instead of an inline <Link muted><RelativeTime/></Link>. Pure refactor, zero visual change.

Removed

• The now-unused local .Timestamp CSS class and the RelativeTime import from CommentCard.

Rollout strategy

• None; Storybook-only helper change with no published/runtime impact (stories don't ship).

Testing & Reviewing

Storybook-only. Verified the Components/Timeline/Internal → Comment cards story headlessly: all comment timestamps still render as underlined muted permalinks at both ≥768px and <768px (the responsive collapsed comment form), with zero console errors. prettier / eslint / stylelint / tsc report no new errors.

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

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Latest commit: e101c56

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Pull request overview

Refactors the internal Timeline CommentCard helper to render its permalink timestamp via the shared MutedTime helper (introduced in prior Timeline internal helpers work), removing the now-redundant inline Link + RelativeTime composition and its local CSS underline class.

Changes:

• Replace Link + RelativeTime timestamp rendering with <MutedTime date={...} href="#" />.
• Remove the now-unused local .Timestamp CSS class and the RelativeTime import.

Show a summary per file

File	Description
packages/react/src/Timeline/internal/CommentCard.tsx	Switches permalink timestamp rendering to the shared MutedTime helper and drops the direct RelativeTime dependency.
packages/react/src/Timeline/internal/CommentCard.module.css	Removes the local .Timestamp underline rule now covered by MutedTime’s shared styling.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Low