added capture time for every sweep

data_acq_and_processing/common_cpp/ipc/include/shared_types.hpp

@@ -38,6 +38,13 @@ struct SweepTraceBlock {
     std::vector<Complex32> s11{};
     // Complex S21 samples for matching frequency points.
     std::vector<Complex32> s21{};
+    // Monotonic window in which THIS trace's sweep was measured, excluding the
+    // switch drive and settling that preceded it. In a switched matrix the
+    // collection is assembled combo by combo over many milliseconds, so the
+    // collection-level window says nothing about when an individual combo was
+    // measured. Zero on both is a valid "unmeasured" sentinel.
+    std::uint64_t capture_start_ns = 0;
+    std::uint64_t capture_end_ns = 0;
 };
 
 struct RawSweepCollection {