init: 클린 아키텍처 백엔드

src/shared-contract/CLAUDE.md

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+# shared-contract — skeleton-wide operational contract
+
+## Registered identity
+
+- Module ID: `shared-contract`
+- Gradle path: `:shared-contract`
+- Focused test: `./gradlew :shared-contract:test --console=plain`
+- Runtime baseline: Java 21; repository framework baseline: Spring Boot 4.0.0.
+- Registry SSOT: `.harness/project/modules.yaml`.
+
+Package root: `dev.caskeleton.shared`.
+
+Design decisions previously kept as code comments (error-code classification, response
+envelope shape, metric cardinality bounds, tracing seam, domain-context propagation) live in
+[README.md](README.md). This file stays the SSOT for module rules.
+
+## Responsibility
+- Response envelope (`response/Envelope`, `response/ApiError`, `response/BulkEnvelope`, `response/BulkItemResult`).
+- Error code contract (`error/ApiErrorCode` interface, `error/OperationalError` enum).
+- Cross-cutting mapper sentinel (`error/MappingException`).
+- Request value contract (`request/Patch`).
+- Tracing contract types (`tracing/TraceParent`, `tracing/BaggageAllowlist`,
+  `tracing/SpanErrorRecorder`) — W3C `traceparent` value type, baggage allowlist,
+  and the span-error-recording seam (feature-distributed-tracing-contract; the OTel
+  tracer runtime is a fork-activated seam, so these stay Java-stdlib-only).
+
+## Allowed
+- Java standard library ONLY. No Spring, no Jackson, no JPA imports.
+
+## Forbidden
+- business/domain concept (domain error codes belong in the consuming module).
+- framework imports (HTTP status is expressed as transport-neutral `int`; the web module maps it).
+
+## Test
+```bash
+cd src
+./gradlew :shared-contract:test
+```