feat(net): add reliability layer, state sync, and client interpolation

- ReliableChannel: sequence numbers, ACK, retransmission, RTT estimation
- OrderedChannel: in-order delivery with out-of-order buffering
- Snapshot serialization with delta compression (per-field bitmask)
- InterpolationBuffer: linear interpolation between server snapshots
- New packet types: Reliable, Ack, Snapshot, SnapshotDelta

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/voltex_net/src/lib.rs

@@ -2,8 +2,14 @@ pub mod packet;
 pub mod socket;
 pub mod server;
 pub mod client;
+pub mod reliable;
+pub mod snapshot;
+pub mod interpolation;
 
 pub use packet::Packet;
 pub use socket::NetSocket;
 pub use server::{NetServer, ServerEvent, ClientInfo};
 pub use client::{NetClient, ClientEvent};
+pub use reliable::{ReliableChannel, OrderedChannel};
+pub use snapshot::{Snapshot, EntityState, serialize_snapshot, deserialize_snapshot, diff_snapshots, apply_diff};
+pub use interpolation::InterpolationBuffer;