chore: add changeset for middleware system

[AlemTuzlak]

Summary

• Adds changeset for the middleware system feature merged in feat: tanstack ai middleware #318
• Minor bump for @tanstack/ai (new middlewares subpath, content guard middleware)
• Minor bump for @tanstack/ai-event-client (initial release, extracted devtools middleware)
• Patch bump for @tanstack/ai-client and @tanstack/ai-devtools (event type and UI updates)

Summary by CodeRabbit

• New Features
  • Introduced a composable middleware system for chat applications with configurable hooks (onStart, onIteration, onChunk, onToolPhaseComplete, onFinish)
  • Added content guard and tool cache middleware options
  • Released a new event client package for improved modularity
  • Enhanced DevTools with middleware-aware event handling and timeline visualization

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

A new middleware system is introduced for TanStack AI with composable chat middleware architecture, including contentGuardMiddleware and toolCacheMiddleware. The devtoolsMiddleware is extracted into a standalone @tanstack/ai-event-client package. Event types and DevTools UI are updated to support middleware-aware event handling.

Changes

Cohort / File(s)	Summary
Middleware System Changelog .changeset/middleware-system.md	Documents introduction of new middleware system, extraction of devtoolsMiddleware to separate package, middleware hooks (onStart, onIteration, onChunk, onToolPhaseComplete, onFinish), and updates to event types and DevTools UI.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A middleware dance, so neat and clean,
Hooks and chains in between,
DevTools spin-off, light and free,
Chat flows smooth as can be! 🌱✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title accurately describes the primary change—adding a changeset for the middleware system feature.
Description check	✅ Passed	The PR description clearly explains the changeset additions and version bumps for all affected packages, though it omits the formal template sections.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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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 chore/middleware-changesets

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