Fixes#2462
## Summary
Removes the per-object `VirtualHairInfo` heap wrapper for mobile/corpse hair. Hair is now stored **inline** on `Mobile` and `Corpse` as `int _hairItemId` / `int _hairHue` plus a lazily-allocated, **non-serialized** ephemeral `Serial _hairSerial` (in the high virtual-serial range) — and likewise for facial hair. The `VirtualHairInfo` class is deleted, with a **lossless** save migration.
This delivers three things:
1. **Fixes a hair-removal bug.** `Delta(MobileDelta.Hair)` is deferred (it enqueues; `ProcessDeltaQueue` runs later in the tick). The old `HairItemID = 0` setter nulled `_hair` *immediately*, so by the time `ProcessDelta` built the remove packet the equipped virtual serial was already gone — the old `??=` code then re-materialized a **fresh** serial (≠ the equipped one), so clients never removed the right entity, and it left a phantom ItemId-0 object behind. The serial now lives on the entity and **persists across removal**, so remove packets carry the correct serial.
2. **Lightens the entity.** No heap hair object; bald mobiles allocate nothing (the serial is minted lazily only when hair is present). This was the original reason `HairItemID`/`HairHue` exist.
3. **Removes `VirtualHairInfo` entirely**, keeping the high-range virtual serial behavior.
## How
- **Mobile** (manual serialization): inline `_hairItemId/_hairHue/_hairSerial` (+facial); lazy `HairSerial`/`FacialHairSerial`; `ProcessDelta` reads those. Serialization **v36 → v37** — the v30-v37 deserialize is unified, reading the legacy per-hair `VirtualHairInfo` version int only when `version < 37`. Setting item id to 0 clears the hue (matching the old object-nulling) while retaining the serial.
- **Corpse** (codegen serialization): decomposed to `[SerializableField] int _hairItemId/_hairHue` (+facial) + ephemeral serial; **v16 → v17** with `MigrateFrom(V16Content)`.
- **Lossless migration:** the loader validates exact byte length, and the old corpse hair is a presence-bool-gated block, so a tiny **migration-only** `LegacyHairInfo` reader (no runtime role) consumes the legacy `[bool][int ver][int itemId][int hue]` bytes. Frozen `Corpse.v14/v15/v16.json` are retyped to it; `v17.json` describes the new int fields.
- All consumers updated to discrete accessors: `OutgoingMobilePackets`, `CorpsePackets`, corpse subclasses (`MilitiaFighterCorpse`, `SchmendrickApprenticeCorpse`), and the packet test mirrors.
- `VirtualHair.cs` renamed to `OutgoingVirtualHairPackets.cs` (the only type left in it after `VirtualHairInfo` was removed).
## Test Plan
- [x] Full solution build: **0 warnings, 0 errors** (`TreatWarningsAsErrors`).
- [x] `Server.Tests`: **708 passed** (incl. new `RemoveHairUsesEquippedSerial` / `RemoveFacialHairUsesEquippedSerial` proving the serial survives removal + hue clears).
- [x] `UOContent.Tests` corpse/hair: **6 passed** (incl. `CorpseHairMigrationTests` asserting the legacy hair bytes are consumed exactly — the loader's length invariant).
- [x] Generated migration code inspected: V14/V15/V16 readers consume the legacy block byte-for-byte; serial never written to disk.
## Upgrade notes
- Old Mobile (v30–v36) and Corpse (v13–v16) saves load losslessly.
- Minor cosmetic-only change: `SchmendrickApprenticeCorpse` hair/facial-hair RNG draws shift order within each pair (same draw count); irrelevant for a quest NPC corpse.
> [!IMPORTANT]
> **Breaking Changes**
> - DecodePacket and EncodePacket delegates replaced with IClientEncryption interface
> - NetState.Connection (Socket) replaced with internal RingSocket management
> - NetState.RecvPipe and NetState.SendPipe removed (buffers managed internally)
## Summary
Upgrades the networking stack from PollGroup-based I/O to io_uring, significantly improving I/O performance on Linux.
This also adds native client encryption support for encrypted UO clients.
## Major Changes
io_uring Networking Architecture
- Replaced PollGroup with IORingGroup for async socket I/O operations
- Removed Pipe.cs (mirrored ring buffer) and TcpServer.cs in favor of RingSocketManager
- Added NetState.Network.cs - centralized network infrastructure handling accept, recv, send, and disconnect
completions
- Added SocketHelper.cs - platform-specific socket utilities for raw socket handle operations (getpeername,
getsockname)
- Buffer management now handled by RingSocketManager with configurable slab allocation
### Client Encryption Support
- Added full encryption stack in Network/Encryption/:
- EncryptionConfig.cs - configurable encryption modes (None, Unencrypted, Encrypted, Both)
- EncryptionManager.cs - encryption detection and initialization for login/game packets
- LoginEncryption.cs - handles login packet encryption with version-derived keys
- GameEncryption.cs - handles game server encryption using Twofish
- TwofishEngine.cs - optimized Twofish block cipher implementation
- LoginKeys.cs - encryption key table for client versions
- IClientEncryption.cs - interface for client encryption implementations
### NetState Improvements
- Replaced Socket Connection with RingSocket _socket for managed socket lifecycle
- Changed from GCHandle polling to event-based completion processing
- Disconnect handling now properly waits for pending sends to flush
- Simplified connecting socket management using lazy queue removal
### Configuration
- New settings: network.encryptionMode and network.encryptionDebug
- Encryption mode flags: Unencrypted, Encrypted, or Both
### Dependencies
- Replaced PollGroup NuGet package with IORingGroup
- Linux requires liburing-dev / liburing-devel package
### Test plan
- Verify server starts and accepts connections on Linux with io_uring
- Verify server starts and accepts connections on Windows (fallback to IOCP)
- Test unencrypted client connections (ClassicUO with encryption disabled)
- Test encrypted client connections if available
- Verify graceful disconnect flushes pending data
- Confirm CI builds pass on all target platforms
### Summary
* Added World.NewVirtual for creating virtual serial numbers
* Reserved range 0x7EEEEEEE to 0x7FFFFFFF for virtual serials
* Hair and Facial hair (for mobiles) now use virtual serials instead of FakeSerial() functions
* Consolidated virtual hair to a single `VirtualHairInfo` class.
Corpse hair and facial hair now persists across save/load and hair and facial hair no longer teleport to newest corpse.
## Breaking Changes
Incoming packet registration signature has changed to:
```cs
delegate* void OnReceiveCallback(NetState state, SpanReader reader, int packetLength);
IncomingPackets.Register(int packetID, int length, bool ingame, OnReceiveCallback onReceive);
```
For example, an incoming packet handler signature would now look like this:
```cs
public static void SomeIncomingPacket(NetState state, SpanReader reader, int packetLength)
{
// Parse the data
}
```
## Summary
Updates the network Pipe class to use a mirrored memory technique. This technique involves mapping the same physical memory to two contiguous virtual memory spaces so the byte buffer appears duplicated. This allows writing to a double-sized array to wrap around without the need for the `CircularBuffer` classes.
In practice this allows us to use `Span<byte>` as if the buffer was a regular array.
### Bug Fixes
- [X] Fixes bad fixed length string parsing
