kmb-wire: Binary wire protocol for Kimberlite

This crate defines the binary wire protocol used for client-server communication in Kimberlite.

Frame Format

┌─────────┬─────────┬──────────┬──────────┬──────────────────┐
│ Magic   │ Version │ Length   │ Checksum │     Payload      │
│ (4 B)   │ (2 B)   │ (4 B)    │ (4 B)    │     (var)        │
└─────────┴─────────┴──────────┴──────────┴──────────────────┘

• Magic: 0x56444220 ("VDB ")
• Version: Protocol version (currently 1)
• Length: Payload length in bytes (max 16 MiB)
• Checksum: CRC32 of payload
• Payload: Bincode-encoded message

Message Types

Messages are either requests (client → server) or responses (server → client). Each request has a corresponding response type.