Market router

The router is a stateless contract that runs a list of calls in one invocation and can fill the order that the first call creates. Its symbol is RouterContract, and it has seven entry points, four plain and three with a relayer fee. Any invoker may call each of them. The router writes no storage and needs no setup, so one deployed instance serves every market.

Page	What it holds
Batches and fills	The Call struct, the strict and the isolated batch rules, the outcome encoding, the first-call convention, the result vector shape, the two host traps, and multicall, multicall_try, create_and_fill, create_and_try_fill.
Fee abstraction	The signed prefix and the unsigned tail, the fee leg and the allowance it wipes, the fee_collected event, the fee error codes, the one instance read, and multicall_with_fee, create_and_fill_with_fee, create_and_try_fill_with_fee.