Address PR review nits and UB concerns

Co-authored-by: Andrey G <networmix@gmail.com>

Author: cursoragent

include/netgraph/core/cost_utils.hpp

@@ -17,8 +17,9 @@ namespace netgraph::core {
   return static_cast<Cost>(std::numeric_limits<Cost>::max() - 1);
 }
 
-// Saturating add for path costs. If either argument is "infinity" (max), or
-// the sum would overflow, returns cost_finite_max().
+// Saturating add for path costs.
+// - If either argument is "infinity" (cost_max), returns cost_max.
+// - If finite addition would overflow, returns cost_finite_max.
 [[nodiscard]] inline constexpr Cost saturating_cost_add(Cost a, Cost b) noexcept {
   if (a == cost_max() || b == cost_max()) return cost_max();
   if (a >= cost_finite_max() || b >= cost_finite_max()) return cost_finite_max();

src/shortest_paths.cpp

@@ -228,8 +228,8 @@ shortest_paths_core(const StrictMultiDiGraph& g, NodeId src,
     return {std::move(dist), std::move(dag)};
   }
 
-  std::vector<int> seen(static_cast<std::size_t>(N), 0);
-  int seen_token = 0;
+  std::vector<std::uint32_t> seen(static_cast<std::size_t>(N), 0u);
+  std::uint32_t seen_token = 0u;
   auto parent_reaches_child_via_pred_links = [&](NodeId parent, NodeId child) {
     if (parent == child) return true;
     ++seen_token;

tests/cpp/flow_policy_tests.cpp

@@ -351,7 +351,7 @@ TEST(FlowPolicyCore, EqualBalanced_ShortestPath_IgnoresHigherCostTier) {
   expect_edge_flows_by_uv(fg, {{0,1,10.0}, {1,4,10.0}, {0,2,0.0}, {2,4,0.0}});
 }
 
-TEST(FlowPolicyCore, MaxPathCostFactor_DoesNotOverflowAndRejectValidPath) {
+TEST(FlowPolicyCore, MaxPathCostFactor_DoesNotOverflowOrRejectValidPath) {
   const auto kMax = std::numeric_limits<Cost>::max();
   // Single edge with very large cost; max_path_cost_factor should not overflow
   // and incorrectly reject this valid path.

tests/cpp/max_flow_tests.cpp

@@ -243,7 +243,8 @@ TEST(MaxFlow, EqualBalanced_ZeroCostCycleStillFindsFeasibleFlow) {
   MaxFlowOptions opts_eq;
   opts_eq.placement = FlowPlacement::EqualBalanced;
   opts_eq.shortest_path = false;
-  auto [total_eq, __] = algs.max_flow(gh, 0, 3, opts_eq);
+  auto [total_eq, unused_summary_eq] = algs.max_flow(gh, 0, 3, opts_eq);
+  (void)unused_summary_eq;
   EXPECT_NEAR(total_eq, 1.0, 1e-9)
       << "Equal-balanced should not collapse to zero flow on zero-cost cycle";
 }
@@ -699,7 +700,8 @@ TEST(MaxFlow, PlacementModes_EqualCapacity_IdenticalResult) {
   MaxFlowOptions opts_eq;
   opts_eq.placement = FlowPlacement::EqualBalanced;
   opts_eq.shortest_path = true;
-  auto [total_eq, __] = algs.max_flow(gh, 0, 3, opts_eq);
+  auto [total_eq, unused_summary_eq] = algs.max_flow(gh, 0, 3, opts_eq);
+  (void)unused_summary_eq;
 
   // Both should saturate both paths
   EXPECT_NEAR(total_prop, 20.0, 1e-9);