fix(docs): update an outdated middleware example

[Dmytro Tiapukhin (eddienubes)]

Changelog

• Introduces a tiny update to a middleware usage example
  Middleware hooks don't have controls parameter injected into them anymore.
  My LLM accidentally pointed out that I should be using controls.terminate to terminate the agent loop referring to this line. However, it's not actual anymore according to the types.

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🦋 Changeset detected

Latest commit: a2e58c3

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

This PR includes changesets to release 1 package

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langchain	Patch

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[Copilot]

Pull request overview

Updates the middleware JSDoc example to reflect the current middleware hook signature where controls is no longer injected into hooks.

Changes:

• Updates beforeModel example signature to remove the controls parameter.
• Replaces controls.terminate(...) with throwing an error in the example.

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[Christian Bromann (christian-bromann)]

Great catch 👌