5177db25b0
Real ShardRuntimeServicer process bound to a real localhost socket, driven by a generated ShardRuntimeStub over grpc.insecure_channel from a separately spawned subprocess. Proves direct-hop and opaque-relay (exact captured request bytes re-sent, no reinterpretation) produce byte-identical server responses, cross-checked against an independent server-side wire capture. Fails closed on the required negative paths: stale route epoch, expired deadline, malformed/non-tiling fragments, checksum failure, exhausted flow-control credit (with in-band top-up), duplicate idempotency steps (acked, not re-applied), and cancel — both in-band CancelSignal (single work item vs whole session) and the out-of-band unary Cancel RPC, including a Cancel that races ahead of SessionOpen. Supersedes the earlier in-memory fake-seam approach for this ticket, which a policy audit rejected under the no-fake-data rule; that code is not reintroduced. Evidence README rewritten to describe the actual files. 11 passed in tests/test_shard_runtime_harness.py.