refactor(node): remove dead code in event source and head sync (leanEthereum#836)

Three unused items, all verified to have zero live call sites:

- set_block_by_slot_lookup setter on the live event source: never
  called anywhere. Its only sibling lookup field on the request
  handler is set directly. Removing it leaves the AsyncBlockBySlotLookup
  import unused, so drop that too.
- connection parameter on the status-exchange helper: status goes
  through the reqresp client, the connection is never read.
- peer_id parameter on the descendant-processing helper: threaded in
  and documented but never read in the body.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tcoratger

src/lean_spec/node/networking/client/event_source/live.py

@@ -81,7 +81,6 @@
 from lean_spec.node.networking.gossipsub.types import TopicId
 from lean_spec.node.networking.reqresp.handler import (
     REQRESP_PROTOCOL_IDS,
-    AsyncBlockBySlotLookup,
     AsyncBlockLookup,
     CurrentSlotLookup,
     ReqRespServer,
@@ -329,20 +328,6 @@ def set_block_lookup(self, lookup: AsyncBlockLookup) -> None:
         """
         self._reqresp_handler.block_lookup = lookup
 
-    def set_block_by_slot_lookup(self, lookup: AsyncBlockBySlotLookup) -> None:
-        """
-        Set the callback for looking up canonical blocks by slot.
-
-        Used by the inbound ReqResp handler to serve BlocksByRange requests.
-
-        The callback MUST consult fork choice.
-        It returns the canonical block at that slot, or None for empty slots.
-
-        Args:
-            lookup: Async function from Slot to SignedBlock or None.
-        """
-        self._reqresp_handler.block_by_slot_lookup = lookup
-
     def set_current_slot_lookup(self, lookup: CurrentSlotLookup) -> None:
         """
         Set the callback returning the node's current slot.
@@ -582,7 +567,7 @@ async def dial(self, multiaddr: str) -> PeerId | None:
             task.add_done_callback(self._gossip_tasks.discard)
 
             # Exchange status.
-            await self._exchange_status(peer_id, connection)
+            await self._exchange_status(peer_id)
 
             # Set up gossipsub stream for full protocol support.
             await self._setup_gossipsub_stream(peer_id, connection)
@@ -698,17 +683,12 @@ async def _handle_inbound_connection(self, connection: QuicConnection) -> None:
 
         logger.info("Accepted connection from peer %s", peer_id)
 
-    async def _exchange_status(
-        self,
-        peer_id: PeerId,
-        connection: QuicConnection,
-    ) -> None:
+    async def _exchange_status(self, peer_id: PeerId) -> None:
         """
         Exchange Status messages with a peer.
 
         Args:
             peer_id: Peer identifier.
-            connection: QuicConnection to use.
         """
         if self._our_status is None:
             logger.debug("No status set, skipping status exchange")

src/lean_spec/node/sync/head_sync.py

@@ -182,7 +182,6 @@ async def on_gossip_block(
             logger.debug("on_gossip_block: parent found, processing")
             return await self._process_block_with_descendants(
                 block=block,
-                peer_id=peer_id,
                 store=store,
             )
 
@@ -200,7 +199,6 @@ async def on_gossip_block(
     async def _process_block_with_descendants(
         self,
         block: SignedBlock,
-        peer_id: PeerId | None,
         store: Store,
     ) -> tuple[HeadSyncResult, Store]:
         """
@@ -211,7 +209,6 @@ async def _process_block_with_descendants(
 
         Args:
             block: Block to process.
-            peer_id: Peer that sent the block.
             store: Current store.
 
         Returns: