fix(medcare_bridge): drop the test temp dir instead of mem::forget

CodeRabbit (PR #582): the test helper leaked a temp dir via
std::mem::forget(tmp) on every call. hydrate_once_sync parses the TTL into
the in-memory OntologyRegistry, so the dir isn't needed afterward — let it
drop. medcare_bridge tests 8/8 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EYvNjD8M8LMNYbRy3gq2FP

Author: claude

crates/lance-graph-ontology/src/bridges/medcare_bridge.rs

@@ -83,7 +83,10 @@ ogit.Healthcare:Patient
         registry
             .hydrate_once_sync(tmp.path(), &["Healthcare"])
             .unwrap();
-        std::mem::forget(tmp);
+        // `hydrate_once_sync` parses the TTL into the in-memory registry, so
+        // the temp dir is no longer needed — let it drop (no leak). The
+        // earlier `std::mem::forget(tmp)` kept it alive unnecessarily
+        // (CodeRabbit, PR #582).
         registry
     }