Fix assert types

[tmcw]

This clarifies that assert can be used with 2-3 arguments, but not with a single argument. The second argument must be the status code as a number.

• Fixes Types for fastify.assert() are incorrect #214

Checklist

• run npm run test && npm run benchmark --if-present
• tests and/or benchmarks are included
• [-] documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[Copilot]

Pull request overview

This PR updates the TypeScript typings for fastify.assert() (and its helper methods) to reflect the actual runtime contract: the status code must be provided as the second argument, with an optional message as the third.

Changes:

• Make code a required parameter (typed as number) across assert, assert.ok, and related assertion helpers in types/index.d.ts.
• Update types/index.test-d.ts to use the new required-code calling patterns.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
types/index.d.ts	Tightens the Assert function/method signatures to require a status code.
types/index.test-d.ts	Updates the type-level tests to call assert APIs with the required status code parameter.

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[mcollina]

lgtm