feat: show zone resolver diagnostics

docs/graph-explorer-contract.md

@@ -182,6 +182,12 @@ Useful warnings for the graph explorer include:
 - local-only surfaces that appear in shared or production scenarios;
 - conflicting port or host claims within the same deployment scenario.
 
+Zone resolvers should also expose scoped diagnostics in zone detail panels. The
+initial diagnostic set includes empty zone seed sets, visible nodes matched by
+multiple zone definitions, and edges crossing zone boundaries. Attraction
+diagnostics such as multiple attraction candidates or depth-limit stops belong
+to the same resolver diagnostic channel when attraction rules are enabled.
+
 ## Repo-Scoping Compatibility
 
 Repo-scoping can adapt without a rewrite because its current graph payload