[helmipradita]

Fixes #321.

Problem

When registering the plugin with the namespace option (e.g. namespace: 'auth'), runtime decorators are registered on FastifyRequest (request.authJwtVerify, request.authJwtDecode) and FastifyReply (reply.authJwtSign).

However, the documentation and type definitions provided only FastifyJwtNamespace, a union type merging both request and reply functions, and instructed users to extend FastifyInstance:

declare module 'fastify' {
  interface FastifyInstance extends FastifyJwtNamespace<{namespace: 'auth'}> {}
}

This caused:

1. FastifyInstance incorrectly receiving request/reply methods.
2. FastifyRequest and FastifyReply not receiving their respective decorator typings, making calls like request.authJwtVerify() or reply.authJwtSign() fail TypeScript compilation.

Fix

• Export FastifyJwtRequestNamespace and FastifyJwtReplyNamespace helper types scoped specifically to request and reply interfaces.
• Keep FastifyJwtNamespace as an intersection of both helpers for backwards compatibility.
• Update README.md documenting the correct augmentation pattern for FastifyRequest and FastifyReply.
• Add type tests in types/namespace.tst.ts asserting that request.authJwtVerify, request.authJwtDecode, and reply.authJwtSign are properly typed.

Checklist

• run npm test — lint clean, 199/199 unit tests (100% coverage), 49/49 type assertions
• tests are included
• documentation is changed or added
• commit message and code follows the Developer's Certificate of Origin and the Code of Conduct

[SameRainbows]

Nice work separating the namespace decorator typings.

A few key points verified:

• Preserving FastifyJwtNamespace as the intersection FastifyJwtRequestNamespace<C> & FastifyJwtReplyNamespace<C> maintains complete backwards compatibility for existing codebases.
• Cleanly addresses #321 by allowing users to augment FastifyRequest and FastifyReply independently without polluting FastifyInstance.
• Fallback logic for custom method keys (jwtDecode, jwtVerify, jwtSign) behaves as expected when only a subset of method names are overridden.
• All 15 CI matrix jobs across Node 20 through Node 26 (Ubuntu, macOS, Windows) and tstyche assertions pass cleanly.