fix(tdigest): fix incorrect min/max default initialization

CentroidsWithDelta struct was default-initializing min and max to 0,
which caused incorrect behavior when merging empty tdigests. Also
delete Reset({}) overload to prevent accidental misuse.

Assisted-by: Claude Code:glm-5

Author: Tangruilin

src/types/tdigest.cc

@@ -355,6 +355,7 @@ class TDigest {
   void Merge(const std::vector<TDigest>& others);
   void Add(const std::vector<double>& items);
   void Reset(const CentroidsWithDelta& centroid_list);
+  void Reset(std::initializer_list<CentroidsWithDelta>) = delete;
   void Reset();
   CentroidsWithDelta DumpCentroids() const;
 

src/types/tdigest.h

@@ -22,6 +22,7 @@
 
 #include <fmt/format.h>
 
+#include <limits>
 #include <map>
 #include <numeric>
 #include <variant>
@@ -47,10 +48,10 @@ struct Centroid {
 
 struct CentroidsWithDelta {
   std::vector<Centroid> centroids;
-  uint64_t delta;
-  double min;
-  double max;
-  double total_weight;
+  uint64_t delta = 0;
+  double min = std::numeric_limits<double>::max();
+  double max = std::numeric_limits<double>::lowest();
+  double total_weight = 0;
 };
 
 StatusOr<CentroidsWithDelta> TDigestMerge(const std::vector<CentroidsWithDelta>& centroids_list, uint64_t delta);