feat(nextjs): Drop support for next v13 and v14

[panteliselef]

Description

This PR raises the minimum supported Next.js version to 15.2.3, removing most legacy compatibility code for Next.js 13 and 14.

• Removed the startTransition wrapper around router.refresh() that was only needed for Next.js 13. Dropped the __clerk_internal_invalidateCachePromise mechanism that coordinated promise resolution with transition state. Removed the isPending state tracking from useTransition since we no longer wrap operations in transitions. The __unstable__onBeforeSetActive hook now directly calls invalidateCacheAction() (or skips it for Next.js 15+ sign-outs).
• Cleaned up the deprecation warning that alerted users about Next.js 13.x and 14.0.x support ending
• Cleaned up version detection helpers (isNext13, isNextWithUnstableServerActions) that gated legacy behavior
• Simplified keyless feature flag: No longer needs to check for unstable server action versions
• Removed version checks in useInternalNavFun for handling shallow routing state
• New peerDependencies: "next": "^15.2.3 || ^16"

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

[changeset-bot]

🦋 Changeset detected

Latest commit: 21e6043

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

This PR includes changesets to release 1 package

Name	Type
@clerk/nextjs	Major

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Project	Deployment	Preview	Comments	Updated (UTC)
clerk-js-sandbox	Ready	Preview	Comment	Nov 10, 2025 8:11pm

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch elef/user-3058-drop-support-for-nextjs-versions-that-are-older-than-1523

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[panteliselef]

!allow-major