[zhuje]

Description

Adds a reusable Divider primitive to @perses-dev/components/next/primitives.

• Implements horizontal and vertical Base UI separators with Perses token-based styling.
• Exports Divider and DividerProps from the primitives barrel.
• Registers Divider in PersesComponents and defaultComponents.
• Adds unit tests, public-export coverage, and Ladle stories for both orientations.

Screenshots

Checklist

• Pull request has a descriptive title and context useful to a reviewer.
• Pull request title follows the [<catalog_entry>] <commit message> naming convention using one of the
  following catalog_entry values: FEATURE, ENHANCEMENT, BUGFIX, BREAKINGCHANGE, DOC,IGNORE.
• All commits have DCO signoffs.

UI Changes

• Changes that impact the UI include screenshots and/or screencasts of the relevant changes.
• Code follows the UI guidelines.
• E2E tests are stable and unlikely to be flaky.
  See e2e docs for more details. Common issues include:
  • Is the data inconsistent? You need to mock API requests.
  • Does the time change? You need to use consistent time values or mock time utilities.
  • Does it have loading states? You need to wait for loading to complete.

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit bf44da0.}