feat: grpc 기능 deep 구현

docs/compatibility/grpc-support-matrix.md

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+# gRPC platform support matrix
+
+What the Stable gRPC platform (`:grpc:*`) is certified against, what it is only checked against, and
+what is merely watched. The distinction is the point: "works with Spring Boot" is not a statement
+anyone can act on.
+
+`GrpcCompatibilityMatrix.caSkeleton()` is the machine-readable form of this table, and
+`GrpcStableReleaseGate` blocks a release when a certified lane has no result or a failing one.
+
+## Lanes
+
+| Lane | Grade | Failure blocks a release |
+| --- | --- | --- |
+| Boot-managed platform (Spring Boot 4.0.8 BOM) | Certified | Yes |
+| proto3 with explicit `optional` | Certified | Yes |
+| `grpc-netty-shaded` | Certified | Yes |
+| `grpc-netty` (unshaded) | Compatibility | No |
+| Upstream gRPC Java version override | Compatibility | No |
+| Protobuf Edition 2024 | Watch | No |
+| Protobuf Edition 2026 | Watch | No |
+
+## Runtime baseline
+
+| | |
+| --- | --- |
+| Java | 21 |
+| Spring Boot | 4.0.8 (the repository baseline; the plans assume 4.1) |
+| io.grpc | `ext.grpcVersion` in `src/build.gradle` |
+| Protobuf | `ext.protobufVersion` in `src/build.gradle` |
+| Stable transport | Netty (shaded) |
+| Stable RPC shapes | Unary, Server Streaming |
+| Stable resolvers | Static, DNS, Unix domain socket |
+| Stable load balancing | `pick_first`, `round_robin` |
+
+## Evidence grades
+
+A capability may only be advertised on evidence of a grade that can establish it.
+`GrpcEvidenceGrade.requireCertifies` enforces this, and `GrpcReleaseEvidence.supports` refuses a
+claim backed by the wrong lane.
+
+| Grade | Lane | Establishes |
+| --- | --- | --- |
+| `CONTRACT` | `grpcInProcessContractTest` | adapter, interceptor order, status mapping, validation, idempotency replay, context propagation |
+| `TRANSPORT` | `grpcNettyContractTest` | HTTP/2, TLS, mTLS, metadata limit, message limit, GOAWAY, keepalive, graceful shutdown |
+| `FAULT` | `grpcFaultTest` | connection loss, completion unknown, partial stream, evidence classifier |
+| `PERFORMANCE` | `grpcPerformanceTest` | latency, stream saturation, executor saturation, drain budget |
+
+In-process results are never transport evidence. The in-process transport does not negotiate TLS,
+does not frame HTTP/2 and does not enforce transport-level limits, so a suite that passes there has
+tested the adapter and not the transport.
+
+## What is not supported
+
+| | Where it lives |
+| --- | --- |
+| Client streaming, bidirectional streaming | `grpc-advanced-streaming` |
+| Manual flow control | `grpc-advanced-streaming` |
+| Hedging | `grpc-advanced-resilience` |
+| Custom name resolver, custom load balancer | `grpc-advanced-resilience` |
+| xDS | `grpc-advanced-resilience` |
+| gRPC-Web, Servlet HTTP/2, Spring Integration, Reactor, Kotlin | `grpc-advanced-compat` |
+| Channelz / CSDS diagnostics | `grpc-advanced-diagnostics` |
+
+## Current release status
+
+Not released. Every `:grpc:*` leaf is `runtime_memberships: []` in the module registry, so the
+platform is build-only: it compiles, its lanes run, and no deployed artifact carries it.
+
+Two release gate inputs are outstanding and are the work between here and a release:
+
+- **Performance baseline.** The performance lane runs and asserts shape — ordered percentiles, a gate
+  that reads them — rather than absolute numbers. A recorded baseline on a known runner is what turns
+  it into a regression gate.
+- **Schema codegen.** No `protoc` runs in this build (ADR-GRPC-002), so the descriptor artifact and
+  the consumer-compile fixture are governed as policy rather than produced from a compiled schema.