Description: Fix compilation with gcc 16
Assisted-By: deepseek-v4.1-flash-free

Index: arb/PROBE/PT_new_design.cxx
===================================================================
--- a/PROBE/PT_new_design.cxx
+++ b/PROBE/PT_new_design.cxx
@@ -1247,7 +1247,7 @@ public:
 };
 
 struct SCP_Less {
-    bool operator()(const SmartCharPtr& p1, const SmartCharPtr& p2) { return &*p1 < &*p2; } // simply compare addresses
+    bool operator()(const SmartCharPtr& p1, const SmartCharPtr& p2) const { return &*p1 < &*p2; } // simply compare addresses
 };
 
 class ProbeCandidates {
