The aggregated attestation pipeline was broken at multiple points,
preventing finalization in multi-node setups:

- Add missing GossipAggregatedAttestationEvent to network events
- Add AGGREGATED_ATTESTATION decoding and dispatch in event sources
- Fix SyncService.publish_aggregated_attestation to use a callback
  instead of a missing method on NetworkRequester
- Wire publish callback directly in Node.from_genesis
- Publish aggregates from ChainService._initial_tick (was discarded)
- Enable test_late_joiner_sync with is_aggregator=True on node 0

- Unpack (store, aggregates) tuple from on_tick and
  aggregate_committee_signatures in fork choice fill framework
- Update attestation target selection tests for the +1 safe_target
  allowance introduced in get_attestation_target

- Remove @pytest.mark.skip from test_mesh_finalization and test_mesh_2_2_2_finalization
- Update store attribute references: latest_new_attestations -> latest_new_aggregated_payloads,
  latest_known_attestations -> latest_known_aggregated_payloads
- test_partition_recovery remains xfail (known sync service limitation)

- Fix test_store_attestations indentation: steps 2-3 were inside for loop,
  causing aggregation to clear signatures before second validator check
- Fix store.py lint: remove blank line after docstring, wrap long line
- Fix type errors: peer_id accepts None for self-produced blocks throughout
  sync pipeline (SyncService, HeadSync, BlockCache)
- Fix formatting in service.py, node_runner.py, test_multi_node.py

Replace fixed 70s duration loops with convergence helpers:
- assert_all_finalized_to: polls until finalization target reached
- assert_heads_consistent: polls until head slots converge
- assert_same_finalized_checkpoint: polls until nodes agree

This fixes CI flakiness where slow machines cause nodes to diverge
during the fixed wait period. Tests now exit early on success and
tolerate slower environments via generous timeouts.

- Increase gossipsub mesh stabilization from 5s to 10s in start_all
  (CI machines need more time for mesh formation before block production)
- Increase finalization timeout from 100s to 150s
- Increase peer connection timeout from 15s to 30s
- Increase pytest timeout from 200s to 300s

The CI failure showed all 3 nodes stuck at finalized slot 0,
indicating gossip mesh wasn't fully formed when services started.

The previous +Slot(1) offset allowed target to equal head when head was
only 1 slot ahead of safe_target, conflating fork choice (head vote)
with BFT finality (target vote). This violates the separation between
the two mechanisms.

With strict > safe_target.slot, the target never exceeds safe_target.
Genesis bootstraps naturally: update_safe_target at interval 3 advances
safe_target via 2/3+ head votes, so target progresses by slot 2.

Restore full docstrings for accept_new_attestations and aggregate_committee_signatures
methods to match origin/main. The implementations changed (tuple return types, aggregates
collection), but these docstrings document the overall behavior which remains the same.
No functional change.

…back

The strict > safe_target.slot walkback (without +Slot(1) offset) introduces
a 1-slot delay in attestation target advancement. Targets lag by 1 slot
compared to the old behavior, requiring more time for justification consensus.

Increased finalization timeout from 150s to 180s in both mesh finalization tests.
This gives the protocol enough time (~50-60s vs 30s) to reach finalization
on typical CI machines.

The [6, 6, 0] finalization failure (2 nodes finalized, 1 stuck at genesis)
indicates a gossip mesh formation race condition on slow CI machines.

Changes:
1. Increase mesh stabilization delay from 10s to 15s for slower CI
2. Add assert_heads_consistent check after peer connections to verify
   gossip subscriptions are active (not just peer connections)

This catches nodes that have peer connections but haven't completed
gossip topic subscription handshakes, preventing isolated node scenarios.