feat(timestamp): port pf-v5-timestamp to pf-v6-timestamp element

[adamjohnson]

Summary

• Removes <pf-v5-timestamp>
• Ports <pf-v5-timestamp> to <pf-v6-timestamp> web component for PatternFly v6
• Displays formatted date/time values using Intl.DateTimeFormat via TimestampController
• Supports date-format, time-format, display-suffix, locale, relative, utc, and hour-12 attributes
• New help-text attribute for tooltip trigger styling with keyboard focus (WCAG 2.1.1)
• Default slot for custom display content (e.g. relative time text, prefacing text)
• CSS uses --pf-v6-c-timestamp--* design tokens with inherit color fallback for composability
• Demos: default, basic-formats, custom-format, default-tooltip, custom-content, custom-tooltip, relative-format, relative-format-with-tooltip

Closes #3045

Intentional divergences from React

• tooltip prop replaced by composition with <pf-v5-tooltip> (slot-based composition over config objects)
• shouldDisplayUTC renamed to utc (shorter, idiomatic HTML attribute)
• is12Hour renamed to hour-12 (dash-case per HTML convention; supports hour-12="false")
• date accepts a string (any new Date()-parseable value) instead of a Date object
• children mapped to default slot
• help-text attribute added (not in React) for dashed underline styling and keyboard focusability

Test plan

• npm run test passes
• Demos render correctly at localhost:8000 with ?rendering=chromeless
• Default timestamp displays current date/time
• All format variants (full, long, medium, short) visually match patternfly.org
• Relative time displays correctly for past, present, and future dates
• help-text timestamps show dashed underline and are keyboard-focusable via Tab
• Tooltip text is visible (white on dark) when timestamp is inside <pf-v5-tooltip>
• UTC display appends "UTC" suffix
• Custom slot content replaces formatted time while preserving datetime attribute

Assisted-By: Claude

[changeset-bot]

🦋 Changeset detected

Latest commit: 9bb0f60

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

This PR includes changesets to release 1 package

Name	Type
@patternfly/elements	Major

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[github-actions]

✅ Commitlint tests passed!

More Info

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  "valid": true,
  "errors": [],
  "warnings": [],
  "input": "feat(timestamp): port pf-v5-timestamp to pf-v6-timestamp element"
}

[github-actions]

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