add claude specific configuration and instruction

.claude/rules/testing.md

@@ -0,0 +1,12 @@
+---
+paths: ["**/*.spec.ts", "**/*.type-spec.ts"]
+---
+
+# Test Conventions
+
+- **`*.spec.ts`** — runtime tests. Use Arrange/Act/Assert with `describe`/`it` blocks.
+- **`*.type-spec.ts`** — compile-time type tests. Use `expectTypeOf(x).toEqualTypeOf<T>()` from expect-type.
+- Tests live in `spec/` directories next to the module, one file per operation (e.g., `map.spec.ts`).
+- When adding a new method, create both a `*.spec.ts` and `*.type-spec.ts` for it.
+- Run runtime tests: `pnpm test -- src/{module}/spec/{file}.spec.ts`
+- Run type tests: `pnpm test:types`