[codex] migrate Effect.fn in apps/server/src/checkpointing/Layers/CheckpointDiffQuery.ts

[juliusmarminge]

Summary

• migrate the remaining () => Effect.gen(...) wrapper in apps/server/src/checkpointing/Layers/CheckpointDiffQuery.ts to Effect.fn
• keep this PR scoped to a single file as part of the checklist split

Why

• finish the remaining checklist migrations without batching multiple files into one review
• keep exact-empty-arg Effect.gen wrappers out of the codebase

Validation

• bun fmt
• bun lint
• packages/shared: bun run test src/DrainableWorker.test.ts
• apps/server: bun run test src/provider/Layers/EventNdjsonLogger.test.ts src/provider/Layers/ProviderRegistry.test.ts src/provider/Layers/ProviderService.test.ts src/provider/Layers/ProviderAdapterRegistry.test.ts src/keybindings.test.ts src/open.test.ts
• apps/server: bun run test src/orchestration/projector.test.ts
• apps/server: bun run test src/orchestration/Layers/OrchestrationEngine.test.ts -t "returns deterministic read models for repeated reads"
• apps/server: bun run test src/orchestration/Layers/OrchestrationEngine.test.ts -t "archives and unarchives threads through orchestration commands"
• apps/server: bun run test src/orchestration/Layers/OrchestrationEngine.test.ts -t "streams persisted domain events in order"

Notes

• validation was run from the completed checklist scratch branch before splitting these per-file PRs
• bun run test and bun typecheck at the repo root currently fail in apps/web because @effect/atom-react cannot be resolved
• apps/server still has unrelated pre-existing typecheck failures outside this file

Note

Migrate getTurnDiff in CheckpointDiffQuery to use Effect.fn

Rewrites getTurnDiff in CheckpointDiffQuery.ts from an arrow function wrapping Effect.gen to the Effect.fn("getTurnDiff") form. No logic or generator body changes are made.

^{Macroscope summarized c036667.}

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Note

Low Risk
Pure refactor that changes only how getTurnDiff is wrapped (to Effect.fn) without altering the generator body or diff computation logic; low chance of behavior change beyond instrumentation/naming effects.

Overview
Refactors CheckpointDiffQuery’s getTurnDiff in CheckpointDiffQuery.ts from an arrow function returning Effect.gen to the named Effect.fn("getTurnDiff") form.

No functional logic changes were made to turn-diff computation, validation, or error handling; this is a wrapper/style migration to the standardized Effect.fn pattern.

^{Written by Cursor Bugbot for commit c036667. This will update automatically on new commits. Configure here.}

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