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-17.md

@@ -0,0 +1,53 @@
+# Session 17: Store Interfaces & Memory Store
+
+## Summary
+
+Storage abstraction layer (interfaces for streams and consumers) and the in-memory storage implementation. Also includes disk availability checks.
+
+## Scope
+
+| Go File | Features | Feature IDs | Go LOC |
+|---------|----------|-------------|--------|
+| server/store.go | 31 | 3164–3194 | 391 |
+| server/memstore.go | 98 | 2068–2165 | 2,434 |
+| server/disk_avail.go | 1 | 827 | 15 |
+| server/disk_avail_netbsd.go | 1 | 828 | 3 |
+| server/disk_avail_openbsd.go | 1 | 829 | 15 |
+| server/disk_avail_solaris.go | 1 | 830 | 15 |
+| server/disk_avail_wasm.go | 1 | 831 | 3 |
+| server/disk_avail_windows.go | 1 | 832 | 3 |
+| **Total** | **135** | | **2,879** |
+
+## .NET Classes
+
+- `StorageEngine` — storage interface definitions (`StreamStore`, `ConsumerStore`)
+- `StoreMsg` — stored message type
+- `StorageType`, `StoreCipher`, `StoreCompression` — storage enums
+- `DeleteBlocks`, `DeleteRange`, `DeleteSlice` — deletion types
+- `JetStreamMemoryStore` — in-memory stream store
+- `ConsumerMemStore` — in-memory consumer store
+- `DiskAvailability` — disk space checker (platform-specific)
+
+## Test Files
+
+| Test File | Tests | Test IDs |
+|-----------|-------|----------|
+| server/store_test.go | 17 | 2941–2957 |
+| server/memstore_test.go | 41 | 2023–2063 |
+| **Total** | **58** | |
+
+## Dependencies
+
+- Session 01 (Foundation Types)
+- Session 02 (Utilities)
+
+## .NET Target Location
+
+- `dotnet/src/ZB.MOM.NatsNet.Server/JetStream/Storage/`
+
+## Notes
+
+- Store interfaces define the contract for both memory and file stores
+- MemStore is simpler than FileStore — good to port first as a reference implementation
+- Disk availability uses platform-specific syscalls — map to `DriveInfo` in .NET
+- Most disk_avail variants can be N/A (use .NET cross-platform API instead)