[vitest-pool-workers] Fix SELF type for RPC workers

[penalosa]

Fixes #9770.

The SELF export in cloudflare:test was typed as Fetcher without a type parameter, which prevented TypeScript from recognizing RPC methods when testing workers that extend WorkerEntrypoint.

This PR adds a ProvidedWorker interface that users can augment to provide their worker's type, allowing SELF to be properly typed as Service<T> for RPC-enabled workers:

import type MyWorker from "./src/index";

declare module "cloudflare:test" {
  interface ProvidedWorker {
    default: typeof MyWorker;
  }
}

// Now SELF will have your RPC methods typed:
const result = await SELF.myRpcMethod("test");

When ProvidedWorker.default is not set, SELF defaults to Fetcher for backward compatibility.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because: This is a type-only change that doesn't affect runtime behavior. Type checking passes via pnpm check --filter @cloudflare/vitest-pool-workers.
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: The type definitions include comprehensive JSDoc comments explaining how to use the new ProvidedWorker interface.

[changeset-bot]

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Latest commit: a811f16

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[claude]

Claude finished @penalosa's task —— View job

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✅ All changesets look good

The changeset .changeset/fix-self-type-for-rpc-workers.md passes all validation criteria:

1. ✅ Version Type: patch is appropriate for a type improvement
2. ✅ Changelog Quality: Clear title and detailed description with usage example
3. ✅ Markdown Headers: No h1/h2/h3 headers used
4. ✅ Analytics: Not applicable (no analytics changes)
5. ✅ Dependabot: Not applicable (not a dependency update)
6. ✅ Experimental features: Not applicable (not experimental)

The changeset follows all formatting guidelines with a clear imperative title, detailed explanation of the problem and solution, and a helpful code example showing how to use the new ProvidedWorker interface.

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commit: a811f16