chore(nextjs): Update middleware check for proxy usage (#7269)

[alexcarpenter]

Description

Backports #7269

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:

Summary by CodeRabbit

• New Features

  • Version-aware Next.js detection to tailor middleware guidance and messaging.

• Bug Fixes

  • Improved middleware location checks and user-facing guidance, including "proxy" wording for Next.js 16+ and updated auth/middleware messages.

• Tests

  • Added tests covering Next.js version detection and conditional messaging across versions.

• Chores

  • Added a changeset entry.

[changeset-bot]

🦋 Changeset detected

Latest commit: cb99641

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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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
clerk-js-sandbox	Skipped		Feb 4, 2026 8:27pm

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commit: cb99641

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a new SDK version utility that detects the installed Next.js major version and exports isNext16OrHigher and middlewareFileReference. Refactors middleware-location detection and error messaging to conditionally include proxy.(ts|js) for Next.js 16+, and threads the parameterized file reference through auth error helpers. Tests were updated to detect Next.js at runtime and assert version-specific messages; a new unit test suite validates the sdk-versions logic. A changelog/changeset file was added.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: updating the Next.js middleware check to support proxy usage, which aligns with the PR's objective of adding runtime detection for Next.js 16+ middleware/proxy file references.

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