Add Effect v4 support for diagnostics, refactors, and piping

[mattiamanzati]

Summary

• Adds comprehensive Effect v4 support across diagnostics, refactors, and piping features
• Introduces new diagnostics: multipleEffectProvide, strictEffectProvide, missingLayerContext
• Extends existing diagnostics (deterministicKeys, leakingRequirements, schemaSyncInEffect) for v4's ServiceMap.Service patterns and updated API surface
• Adds new refactors: layerMagic (automatic layer composition) and structuralTypeToSchema (interface/type alias to Schema class conversion)
• Enhances makeSchemaOpaque and typeToEffectSchema for v4's Codec, DecodingServices, and EncodingServices types
• Adds pipe transformation support for v4 including Effect.fn, nested pipes, and function call conversions

New Diagnostics

multipleEffectProvide — Warns when multiple Effect.provide calls are chained consecutively, suggesting consolidation:

// Before (warns)
program.pipe(Effect.provide(layerA), Effect.provide(layerB))

// After (suggested fix)
program.pipe(Effect.provide(Layer.mergeAll(layerA, layerB)))

strictEffectProvide — Warns when using Effect.provide with a Layer outside of application entry points.

missingLayerContext — Detects missing Layer context requirements in Effect.Service declarations.

New Refactors

layerMagic — Automatically compose and build layers based on service dependencies:

// "Prepare layer" refactor on a Layer expression
// "Build layer" refactor to compose multiple layers

structuralTypeToSchema — Converts TypeScript interfaces and type aliases to Effect Schema classes:

// Before
interface User { name: string; age: number }

// After
class User extends Schema.Class<User>()({ name: Schema.String, age: Schema.Number }) {}

Test plan

• pnpm lint-fix passes
• pnpm check passes (no type errors)
• pnpm test passes (493/493 tests)
• Snapshot tests cover all new diagnostics, refactors, and piping features for v4

🤖 Generated with Claude Code

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🦋 Changeset detected

Latest commit: e99f63b

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	Minor

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