fix(test): wait for full gossip mesh before committee produces (A-1219)

[PhilWindle]

Problem

e2e_p2p_network › should rollup txs from all peers (and add the validators without cheating) (in gossip_network_no_cheat.test.ts) intermittently fails with TimeoutError: Timeout awaiting first checkpoint published — the chain never gets a first checkpoint onto L1 within 120s.

Log analysis

From CI run 6d6e74a70fce8826:

• The test did a blind sleep(8000) for peer discovery, then waited for the first checkpoint. On the 2-CPU runner the gossipsub proposal/checkpoint meshes were not fully formed 8s in.
• The first checkpoint attempt (slot 97, proposer validator-3) reached only 2 of 3 attestations — validators 1 and 2 never received the slot-97 proposal at all (only validator-4 had a live gossip path). No L1 publish was attempted; the proposer aborted locally on the attestation-collection timeout.
• Because that checkpoint never landed, the L1-confirmed chain stayed at genesis, so every later slot rebuilt a competing un-checkpointed block 1 (new archive). The blocks are pruned (archiver:l1-sync: Pruning blocks after block 0 ...), but the prune lands ~1.5 slots after the block is built — later than the next proposal arrives. So peers still holding a not-yet-pruned block 1 rejected the new proposal with block_number_already_exists, never re-executed, never attested — capping every round at 2/3 forever.

Root cause: the gossip mesh wasn't formed when the committee started producing, so the first proposal reached only a subset of the committee. That both starved the first checkpoint of quorum and split the validators onto competing block-1 forks that never re-converge.

Fix

Replace the blind sleep(8000) with waitForP2PMeshConnectivity on the block_proposal, checkpoint_proposal, and checkpoint_attestation topics, requiring a full mesh (N-1 peers per node) so the first proposal reaches the whole committee. The first checkpoint then reaches quorum and lands — after which the chain advances to block 2 and no competing block 1 is ever built.

Also adds a minMeshPeerCount parameter to waitForP2PMeshConnectivity (default 1, preserving existing callers — the helper otherwise only requires a single mesh peer per node, which can leave some committee members unreached at first). Quorum-from-genesis tests pass N-1 for a full mesh.

This is the test-side fix that addresses the trigger. There is a separate, more fundamental product-robustness gap — a single missed checkpoint at the chain tip is unrecoverable because of the block_number_already_exists guard vs. the prune latency — which is consensus-sensitive and tracked separately (related to A-1218); it is intentionally not addressed here.

Testing

• Build, format, lint clean; only the test and its helper changed.
• Not yet run: the full e2e (gossip_network_no_cheat.test.ts, real-time-dependent, ideally under a 2-CPU constraint). The real validation is running it repeatedly and confirming the committee reaches 3/3 and the first checkpoint publishes within the gate.

Closes A-1219.