feat(server): add request-ID middleware for request correlation

[sauagarwa]

Summary

Add request-ID middleware to the gateway server so every request carries a unique, traceable identifier. Uses tower-http's SetRequestIdLayer and PropagateRequestIdLayer with UUID v4 generation, recording the ID in the tracing span and returning it in the x-request-id response header. Client-supplied IDs are preserved (no overwrite).

Related Issue

Closes #932

Changes

• Cargo.toml: Enable request-id feature on the tower-http workspace dependency
• crates/openshell-server/src/multiplex.rs:
  • Add UuidRequestId struct implementing MakeRequestId (UUID v4 via existing uuid crate)
  • Update make_request_span to extract and record x-request-id in the tracing span
  • Add request_id_middleware! macro for consistent layer ordering: SetRequestId → TraceLayer → PropagateRequestId
  • Apply middleware to both gRPC and HTTP inner services in MultiplexService::serve()
  • Add 7 unit tests: UUID generation, uniqueness, response header presence, client ID preservation, per-request uniqueness, gRPC content-type routing, and trace span recording
• crates/openshell-server/tests/multiplex_integration.rs:
  • Add grpc_response_propagates_request_id integration test verifying tonic metadata ↔ HTTP header roundtrip for both server-generated and client-supplied request IDs

Log output before

INFO request{method=POST path=/openshell.v1.OpenShell/CreateSandbox}: response status=200 latency_ms=45
INFO request{method=POST path=/openshell.v1.OpenShell/CreateSandbox}: response status=200 latency_ms=312

Log output after

INFO request{method=POST path=/openshell.v1.OpenShell/CreateSandbox request_id=a1b2c3d4-...}: response status=200 latency_ms=45
INFO request{method=POST path=/openshell.v1.OpenShell/CreateSandbox request_id=e5f6a7b8-...}: response status=200 latency_ms=312

Testing

• mise run pre-commit passes
• Unit tests added/updated (7 new tests in multiplex::tests)
• Integration test added (grpc_response_propagates_request_id)
• Full cargo test -p openshell-server passes (353 tests, 0 failures)
• Verified on running cluster — request IDs appear in all gRPC endpoint logs

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (if applicable)

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[github-actions]

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[sauagarwa]

I have read the DCO document and I hereby sign the DCO.

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[sauagarwa]

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[sauagarwa]

I have read the DCO document and I hereby sign the DCO.

[sauagarwa]

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