ratelimit package

Package ratelimit ports golang.org/x/time/rate (the standard Go token-bucket rate limiter) to an on-chain gno.land realm.

Each caller address owns a token bucket with a fixed capacity (burst) that refills at a steady rate expressed in tokens per block. There is no wall clock on-chain, so runtime.ChainHeight() is the monotonic clock: between two observations at heights `last` and `now`, the bucket gains (now-last)*rate tokens, capped at `burst`. Everything is pure, integer/ float arithmetic over persistent avl state, hence deterministic.