[MegaRedHand]

Summary

GET /eth/v1/events accepted every gloas topic but emitted none of them, so contributoor (ethPandaOps) had nothing to show for our nodes on Sepolia. This emits:

Topic	Emitted when
head_v2	next to every head (pre-gloas with payload_status: "full"), and again for the same block on an empty -> full payload status change
block	unchanged, plus builder_index and block_hash for gloas blocks (absent before)
execution_payload, execution_payload_available	the chain actor imports an envelope
execution_payload_gossip	an envelope passes gossip validation, or POST /eth/v1/beacon/execution_payload_envelopes accepts it
execution_payload_bid, proposer_preferences, payload_attestation_message	passes gossip validation, or the matching POST accepts it

head is deprecated by the specification in favour of head_v2 and is still emitted. docs/rpc.md has the new rows, drops the stale "this build stops at fulu" sentence, and documents the execution_payload_available timing.

Design notes

• Publisher. Bids, preferences and payload attestation messages are validated in ethlambda-p2p and never reach the chain actor, and p2p does not depend on ethlambda-blockchain (which owns EventBus). So ethlambda-network-api gets a GossipEventSink trait and a GossipEvent enum, EventBus implements the trait, and main.rs passes Some(Arc::new(events.clone())) into P2P::spawn (new last parameter). The p2p side is one function, publish_gossip_event, called from Validated::forward on Accept only, behind has_subscribers(). The API handlers already run next to the bus, so they emit directly through a small emit_accepted helper; the bus is an Option<Extension<EventBus>> there so routers built without one (the handlers' own tests) still serve.
• Envelope gossip: sink, not BlockAnnouncement. Accepted gossip envelopes do reach the actor, but new_execution_payload_envelope carries no accepted-versus-queued flag, and gossip also forwards Queued envelopes through it. Following the block_gossip pattern would have meant a new parameter on that trait method and every implementor and test double. The sink already exists for the other three, takes Accept only, and touches one function.
• execution_payload_available. Emitted right after execution_payload, from the same import. The actor imports an envelope only once the payload is verified and every sampled column is stored, which is what the event reports, so there is no later moment to wait for.
• head_v2 dependent roots. current_epoch_dependent_root is the root at start_slot(epoch - 1) - 1 and next_epoch_dependent_root the root at start_slot(epoch) - 1, genesis root on underflow. These are head's previous_duty_dependent_root and current_duty_dependent_root renamed, so they come from the same NewChain::dependent_root.
• payload_status. full for every pre-gloas head. From gloas on it follows Store::head_payload_status, with empty when none is recorded yet. The re-emission is driven by the EventView (the head and its recorded status as last reported), so it fires once per empty -> full transition and nothing else repeats (full -> empty is optional in the specification and left out). Both head_v2 emissions keep the 32-slot recency gate head has.
• version on head_v2 is the head state's fork; the bid, message and preferences wrappers are always gloas.
• block fields are Options with skip_serializing_if, so a pre-gloas block's JSON is byte-identical to before.
• A head move now puts two beacon events on the shared ring instead of one. The existing head tests read through drain, which leaves head_v2 out; the new ones use drain_all.

Test plan

• cargo fmt --all
• cargo clippy -p ethlambda-network-api -p ethlambda-blockchain -p ethlambda-p2p -p ethlambda-rpc -p ethlambda --all-targets --profile release-fast -- -D warnings
• cargo test -p ethlambda-blockchain --profile release-fast --lib -- events: JSON shape of every new payload against the specification examples (field names, quoting, version wrapper), the sink-to-topic mapping, the payload_status label.
• cargo test -p ethlambda-blockchain --profile release-fast --lib -- head_v2 imported_envelope block_event_carries ... and the existing beacon event tests: head_v2 dependent roots across epochs 0 to 2 including underflow, the pre-gloas full, the empty -> full re-emission (and that full -> empty and a repeat do not re-emit), publish_envelope_imported, and the block event's bid fields.
• cargo test -p ethlambda-rpc --profile release-fast --lib -- beacon::: an accepted bid and accepted preferences are announced once in their wrapper, a refused or already-pooled bid is not.
• cargo test -p ethlambda-blockchain --profile release-fast --features beacon-spec-tests --lib -- beacon_envelope against the v1.7.0-beta.2 fixtures: 47 passed, including an_imported_envelope_emits_execution_payload_then_available, which drives the actor's real envelope import.
• Not covered by a test: the p2p publish_gossip_event function, and the payload attestation and envelope POST handlers' emission (same helper as the bid and preferences handlers).