feat(registry): expose Conn() and Path() on registry.DB

Allows external readers (registry_mcp app) to issue raw aggregations
(e.g. fn_list_domains) and inspect the active db path without
duplicating the connection setup logic.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

registry/db.go

@@ -57,3 +57,14 @@ func (db *DB) Drop() error {
 	db.Close()
 	return os.Remove(db.path)
 }
+
+// Conn returns the underlying *sql.DB for callers that need raw SQL access
+// (e.g. registry_mcp for aggregations not covered by Search/Get helpers).
+func (db *DB) Conn() *sql.DB {
+	return db.conn
+}
+
+// Path returns the filesystem path of the database file.
+func (db *DB) Path() string {
+	return db.path
+}