docs(contracts): mark galaxy_repository.proto as intentionally retained for clients

The 2026-06-25 re-review observed that the gateway server no longer uses the
Contracts-generated Galaxy types (it consumes the wire-identical types from the
ZB.MOM.WW.GalaxyRepository package). That made galaxy_repository.proto look like
dead code. It is not: Go/Rust/Java/Python clients compile it by path, the .NET
client consumes Contracts.Proto.Galaxy.* via project reference, and
clients/proto/proto-inputs.json publishes it. Document this at the csproj entry
and in CLAUDE.md so it is not deleted in a future cleanup.

CLAUDE.md

@@ -11,7 +11,7 @@ The architecture is a two-process design — read `gateway.md` before making str
 - **Gateway** (`src/ZB.MOM.WW.MxGateway.Server`, .NET 10, x64): ASP.NET Core gRPC server. Owns the public API, sessions, auth, the Blazor dashboard, and the Galaxy Repository SQL browse RPCs. The Galaxy-browse implementation comes from the shared **`ZB.MOM.WW.GalaxyRepository`** package (`AddZbGalaxyRepository`/`MapZbGalaxyRepository`), not inline code; mxaccessgw adds `GatewayBrowseScopeProvider` (per-key browse-subtree scoping) and a host-side dashboard summary projector. See `A2-galaxyrepository-adoption-handoff.md`. **Never instantiates MXAccess COM directly.**
 - **Worker** (`src/ZB.MOM.WW.MxGateway.Worker`, .NET Framework 4.8, **x86**): one process per session. Owns one MXAccess COM instance on a dedicated STA, pumps Windows messages, and converts COM events to protobuf.
 - **IPC**: gateway↔worker uses one bidirectional named pipe per worker (`mxaccess-gateway-{gatewayPid}-{sessionId}`) with length-prefixed `WorkerEnvelope` protobuf frames. Gateway hosts the pipe server and launches the worker. **gRPC is not used inside the worker** — .NET Framework 4.8 doesn't have a first-class gRPC stack.
-- **Contracts** (`src/ZB.MOM.WW.MxGateway.Contracts`): multi-targets `net10.0;net48` and owns the `.proto` files (`mxaccess_gateway.proto`, `mxaccess_worker.proto`, `galaxy_repository.proto`). All other projects consume the generated types from here. Do not hand-edit anything under `Generated/`.
+- **Contracts** (`src/ZB.MOM.WW.MxGateway.Contracts`): multi-targets `net10.0;net48` and owns the `.proto` files (`mxaccess_gateway.proto`, `mxaccess_worker.proto`, `galaxy_repository.proto`). All other projects consume the generated types from here. Do not hand-edit anything under `Generated/`. Note `galaxy_repository.proto` is intentionally kept here as the generation source for the language clients even though the gateway server consumes the wire-identical Galaxy types from the `ZB.MOM.WW.GalaxyRepository` package — it is not dead code; deleting it breaks all five clients.
 
 The worker must do all MXAccess COM calls on its dedicated STA thread, and the STA loop must pump Windows messages (`MsgWaitForMultipleObjectsEx` + `PeekMessage`/`DispatchMessage`) so MXAccess events deliver. A plain blocking queue on an STA is not enough.
 

src/ZB.MOM.WW.MxGateway.Contracts/ZB.MOM.WW.MxGateway.Contracts.csproj

@@ -26,6 +26,11 @@
     <Compile Remove="Generated\**\*.cs" />
     <Protobuf Include="Protos\mxaccess_gateway.proto" ProtoRoot="Protos" OutputDir="Generated" GrpcOutputDir="Generated" GrpcServices="Both" />
     <Protobuf Include="Protos\mxaccess_worker.proto" ProtoRoot="Protos" OutputDir="Generated" GrpcServices="None" />
+    <!-- galaxy_repository.proto is intentionally retained even though the gateway SERVER now consumes
+         the wire-identical Galaxy types from the ZB.MOM.WW.GalaxyRepository package. This proto is
+         still the generation source of truth for the language clients (Go/Rust/Java/Python compile it
+         by path; the .NET client consumes Contracts.Proto.Galaxy.* via this project reference) and for
+         clients/proto/proto-inputs.json. Removing it breaks all five clients — do not delete. -->
     <Protobuf Include="Protos\galaxy_repository.proto" ProtoRoot="Protos" OutputDir="Generated" GrpcOutputDir="Generated" GrpcServices="Both" />
   </ItemGroup>