[cargopete]

Description

Radios grow memory without bound under relay traffic. Two things in the SDK retain every message ever seen: GossipSubParams.history_length is set to 100000, so go-libp2p-pubsub keeps that many heartbeat windows of full messages in its MessageCache, and seen_msg_ids is a HashSet that is only ever inserted into.

This drops the history_length override back to the gossipsub default and replaces the set with SeenMsgIds, a HashSet plus VecDeque capped at 10000 ids with oldest-first eviction. Gossipsub already discards repeats inside its 1800s seen TTL, so the set only has to outlast that window. The field type on GraphcastAgent changes; nothing in graphops reads it outside the SDK.

Verified with two ping-pong radios on 0.7.4. The stock build climbed to ~330MB RSS over a 15h soak and was still going, with the Go heap almost entirely MessageCache. The patched build stayed flat around 100MB for 6h. test_seen_msg_ids_bounded covers the eviction.

Issue link

graphops/subgraph-radio#150

Checklist

• Are tests up-to-date with the new changes?
• Are docs up-to-date with the new changes? (Open PR on docs repo if necessary)