Fix correctness issues in single-block lookup state machine

- add_peer: replace !=-vs-|= typo so Gloas child-peer additions actually
  propagate back through add_peers_to_lookup_and_ancestors and kick
  continue_requests.
- data_peer_group: return the PeerGroup stored in DataRequestState
  Downloaded/Processing instead of todo!(), so InvalidColumn attribution
  in mod.rs no longer panics on a live error path.
- Restore the original `parent_root != ZERO` guard for the parent-known
  check; the genesis block has no real parent so it must fall through to
  processing rather than panic (was todo!()) or be dropped as Failed.
- Wire envelope_is_known_to_fork_choice as a NoRequestNeeded short-
  circuit at the top of payload_lookup_request.
- Rename gload_child_peers -> gloas_child_peers (typo).
- Drop DataDownloadKind, peek_downloaded_peer_group, DataRequest.slot,
  DownloadedData::Blobs.expected_blobs — all dead per the compiler.
- Update test helpers to send UnknownParentSidecarHeader so the lookup
  test suite compiles and runs under the new manager API.

Tests: phase0 79/79, electra 59/59, fulu 59/59.

beacon_node/network/src/sync/tests/lookups.rs

@@ -1522,7 +1522,12 @@ impl TestRig {
     }
 
     fn trigger_unknown_parent_blob(&mut self, peer_id: PeerId, blob: Arc<BlobSidecar<E>>) {
-        self.send_sync_message(SyncMessage::UnknownParentBlob(peer_id, blob));
+        self.send_sync_message(SyncMessage::UnknownParentSidecarHeader {
+            peer_id,
+            block_root: blob.block_root(),
+            parent_root: blob.block_parent_root(),
+            slot: blob.slot(),
+        });
     }
 
     fn trigger_unknown_parent_column(
@@ -1530,7 +1535,17 @@ impl TestRig {
         peer_id: PeerId,
         column: Arc<DataColumnSidecar<E>>,
     ) {
-        self.send_sync_message(SyncMessage::UnknownParentDataColumn(peer_id, column));
+        let DataColumnSidecar::Fulu(col) = column.as_ref() else {
+            panic!(
+                "trigger_unknown_parent_column is Fulu-only; Gloas columns use the partial-column path"
+            );
+        };
+        self.send_sync_message(SyncMessage::UnknownParentSidecarHeader {
+            peer_id,
+            block_root: col.block_root(),
+            parent_root: col.block_parent_root(),
+            slot: col.slot(),
+        });
     }
 
     fn trigger_unknown_block_from_attestation(&mut self, block_root: Hash256, peer_id: PeerId) {