refactor(simulation): apply rustfmt formatting

Formatting-only changes across server source and test files.
No logic changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/knowledge/registry.rs

@@ -214,11 +214,7 @@ mod tests {
             id_first, id_second,
             "Re-registration must assign a new StableId"
         );
-        assert_eq!(
-            id_second,
-            StableId(1),
-            "Counter advances monotonically"
-        );
+        assert_eq!(id_second, StableId(1), "Counter advances monotonically");
         assert_eq!(registry.len(), 1);
 
         // New mapping is bidirectionally correct