Fix effectGenToFn return type conversion

[mattiamanzati]

Summary

• Fixes the effectGenToFn refactor to correctly convert Effect<A, E, R> return type annotations to Effect.fn.Return<A, E, R> when transforming Effect.gen to Effect.fn
• Previously the refactor kept the original Effect.Effect<...> return type, producing code that doesn't compile
• Resolves the imported Effect module identifier to use in the generated Effect.fn.Return type reference

Example

Before this fix, the refactor would produce:

// Broken output (doesn't compile)
const someFunction = Effect.fn("someFunction")(function* (value: string): Effect.Effect<number, boolean> {
  // ...
})

After this fix:

// Correct output
const someFunction = Effect.fn("someFunction")(function* (value: string): Effect.fn.Return<number, boolean, never> {
  // ...
})

Test plan

• Added test example effectGenToFn_returns.ts with two cases (concise body and generics)
• Verified snapshot outputs show correct Effect.fn.Return<A, E, R> type
• All 491 existing tests pass
• TypeScript type checking passes

Closes #634

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🦋 Changeset detected

Latest commit: 450b28c

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

This PR includes changesets to release 1 package

Name	Type
@effect/language-service	Patch

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