feat: port session 07 — Protocol Parser, Auth extras (TPM/certidp/certstore), Internal utilities & data structures

Session 07 scope (5 features, 17 tests, ~1165 Go LOC):
- Protocol/ParserTypes.cs: ParserState enum (79 states), PublishArgument, ParseContext
- Protocol/IProtocolHandler.cs: handler interface decoupling parser from client
- Protocol/ProtocolParser.cs: Parse(), ProtoSnippet(), OverMaxControlLineLimit(),
  ProcessPub/HeaderPub/RoutedMsgArgs/RoutedHeaderMsgArgs, ClonePubArg(), GetHeader()
- tests/Protocol/ProtocolParserTests.cs: 17 tests via TestProtocolHandler stub

Auth extras from session 06 (committed separately):
- Auth/TpmKeyProvider.cs, Auth/CertificateIdentityProvider/, Auth/CertificateStore/

Internal utilities & data structures (session 06 overflow):
- Internal/AccessTimeService.cs, ElasticPointer.cs, SystemMemory.cs, ProcessStatsProvider.cs
- Internal/DataStructures/GenericSublist.cs, HashWheel.cs
- Internal/DataStructures/SubjectTree.cs, SubjectTreeNode.cs, SubjectTreeParts.cs

All 461 tests pass (460 unit + 1 integration). DB updated for features 2588-2592 and tests 2598-2614.

docs/plans/phases/phase6sessions/session-21.md

@@ -0,0 +1,60 @@
+# Session 21: Streams & Consumers
+
+## Summary
+
+Stream and consumer implementations — the core JetStream data plane. Streams store messages; consumers track delivery state and manage acknowledgments.
+
+## Scope
+
+| Go File | Features | Feature IDs | Go LOC |
+|---------|----------|-------------|--------|
+| server/stream.go | 193 | 3195–3387 | 6,980 |
+| server/consumer.go | 209 | 584–792 | 5,720 |
+| **Total** | **402** | | **12,700** |
+
+## .NET Classes
+
+- `NatsStream` — stream lifecycle, message ingestion, purge, snapshots (193 features)
+- `NatsConsumer` — consumer lifecycle, delivery, ack, nak, redelivery (174 features)
+- `ConsumerAction`, `ConsumerConfig`, `AckPolicy`, `DeliverPolicy`, `ReplayPolicy` — consumer types
+- `StreamConfig`, `StreamSource`, `ExternalStream` — stream types
+- `PriorityPolicy`, `RetentionPolicy`, `DiscardPolicy`, `PersistModeType` — policy enums
+- `WaitQueue`, `WaitingRequest`, `WaitingDelivery` — consumer wait types
+- `JSPubAckResponse`, `PubMsg`, `JsPubMsg`, `InMsg`, `CMsg` — message types
+
+## Test Files
+
+| Test File | Tests | Test IDs |
+|-----------|-------|----------|
+| server/jetstream_consumer_test.go | 161 | 1220–1380 |
+| server/jetstream_leafnode_test.go | 13 | 1403–1415 |
+| server/norace_1_test.go | 100 | 2371–2470 |
+| server/norace_2_test.go | 41 | 2471–2511 |
+| **Total** | **315** | |
+
+## Dependencies
+
+- Session 01 (Foundation Types)
+- Session 02 (Utilities)
+- Session 08 (Client Connection)
+- Session 09 (Server Core Part 1)
+- Session 11 (Accounts)
+- Session 17 (Store Interfaces)
+- Session 19 (JetStream Core)
+
+## .NET Target Location
+
+- `dotnet/src/ZB.MOM.NatsNet.Server/JetStream/`
+
+## Notes
+
+- **This is a multi-sitting session** — 12.7K Go LOC and 315 tests
+- Suggested sub-batching:
+  - **21a**: Stream/consumer types and enums (~40 features, ~500 LOC)
+  - **21b**: NatsStream core (create, delete, purge — ~95 features)
+  - **21c**: NatsStream remaining (snapshots, sources, mirrors — ~98 features)
+  - **21d**: NatsConsumer core (create, deliver, ack — ~90 features)
+  - **21e**: NatsConsumer remaining (redelivery, pull, push — ~84 features)
+  - **21f**: Tests (315 tests)
+- `norace_*_test.go` files contain tests that must run without the Go race detector — these may have concurrency timing sensitivities
+- Consumer pull/push patterns need careful async design in C#