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-20.md

@@ -0,0 +1,70 @@
+# Session 20: JetStream Cluster & Raft
+
+## Summary
+
+Raft consensus algorithm implementation and JetStream clustering — how streams and consumers are replicated across server nodes.
+
+## Scope
+
+| Go File | Features | Feature IDs | Go LOC |
+|---------|----------|-------------|--------|
+| server/raft.go | 198 | 2599–2796 | 4,078 |
+| server/jetstream_cluster.go | 231 | 1520–1750 | 10,098 |
+| **Total** | **429** | | **14,176** |
+
+## .NET Classes
+
+- `RaftNode` — Raft consensus implementation (169 features)
+- `AppendEntry`, `AppendEntryResponse` — Raft log entries
+- `Checkpoint` — Raft snapshots
+- `CommittedEntry`, `Entry`, `EntryType` — entry types
+- `VoteRequest`, `VoteResponse`, `RaftState` — election types
+- `RaftGroup` — Raft group configuration
+- `JetStreamCluster` — cluster-wide JetStream coordination (51 features)
+- `Consumer` (cluster) — consumer assignment tracking (7 features)
+- `ConsumerAssignment` — consumer placement
+- `StreamAssignment`, `UnsupportedStreamAssignment` — stream placement
+- Plus ~69 `JetStreamEngine` methods for cluster operations
+
+## Test Files
+
+| Test File | Tests | Test IDs |
+|-----------|-------|----------|
+| server/raft_test.go | 104 | 2616–2719 |
+| server/jetstream_cluster_1_test.go | 151 | 757–907 |
+| server/jetstream_cluster_2_test.go | 123 | 908–1030 |
+| server/jetstream_cluster_3_test.go | 97 | 1031–1127 |
+| server/jetstream_cluster_4_test.go | 85 | 1128–1212 |
+| server/jetstream_cluster_long_test.go | 7 | 1213–1219 |
+| server/jetstream_super_cluster_test.go | 47 | 1419–1465 |
+| server/jetstream_meta_benchmark_test.go | 2 | 1416–1417 |
+| server/jetstream_sourcing_scaling_test.go | 1 | 1418 |
+| **Total** | **617** | |
+
+## Dependencies
+
+- Session 01 (Foundation Types)
+- Session 08 (Client Connection)
+- Session 09 (Server Core Part 1)
+- Session 14 (Routes)
+- Session 17 (Store Interfaces)
+- Session 19 (JetStream Core)
+
+## .NET Target Location
+
+- `dotnet/src/ZB.MOM.NatsNet.Server/JetStream/Cluster/`
+- `dotnet/src/ZB.MOM.NatsNet.Server/Raft/`
+
+## Notes
+
+- **This is a multi-sitting session** — 14.2K Go LOC and 617 tests (the largest session)
+- Suggested sub-batching:
+  - **20a**: Raft types and election (entries, votes, state — ~30 features)
+  - **20b**: Raft core (log replication, append, commit — ~85 features)
+  - **20c**: Raft remaining (snapshots, checkpoints, recovery — ~83 features)
+  - **20d**: JetStream cluster types and assignments (~30 features)
+  - **20e**: JetStream cluster operations Part 1 (~130 features)
+  - **20f**: JetStream cluster operations Part 2 (~71 features)
+  - **20g**: Tests (617 tests, batched by test file)
+- Raft is the most algorithmically complex code in the server
+- Cluster tests often require multi-server setups — integration test candidates