Account attribute updates

Endpoint: wss://api.testnet.arcus.xyz/v1/ws — one socket multiplexes every channel and RPC request. Click Connect, then send the example subscribe message below to start receiving data.

Per-account attribute state, discriminated by entry type. type: "leverage" entries carry effective leverage per market. type: "feeTier" entries carry account-level fee tier state. Snapshot returns one leverage entry per market plus, when available, one fee tier entry. Streaming delivers one entry for each changed attribute.