fix(federation): drop non-dict entries in PeerRegistry.get

A peer returning a registry list with a stray non-dict entry
(e.g. `[{"name":"foo"}, "junk", 42]`) crashed `aggregate()` at
`dict(e)` with a ValueError. The exception propagated up through
`/registry/global`, 500'ing the response and taking the local hub's
own listings down with it — a direct violation of the module's
'peer failures never block the local response' contract.

Filter non-dict rows out of the returned list at the same fetch-boundary
guard that already coerces non-list bodies to empty. Cache stays clean;
aggregate() sees only well-shaped entries.

Author: Zawwarsami16

zhub/federation.py

@@ -57,6 +57,12 @@ async def get(self, peer_url: str) -> list[dict[str, Any]]:
             if not isinstance(data, list):
                 log.warning("peer %s returned non-list registry; treating as empty", peer_url)
                 data = []
+            else:
+                # Individual non-dict entries (a peer returning
+                # ``[{"name":"x"}, "junk", 42]``) crash aggregate() at
+                # ``dict(e)``; one bad row would 500 /registry/global,
+                # dropping the local hub's own listings too.
+                data = [e for e in data if isinstance(e, dict)]
         except Exception as e:
             log.warning("peer %s unreachable: %s", peer_url, e)
             # Negatively cache the failure: without this a dead peer is