fix: a truncated scan stays truncated, so a hit list with a hole is not reported clean

src/search.hpp

@@ -81,6 +81,7 @@ class BufferSearch {
   int channel_ = -1;
   State state_ = State::Idle;
   bool started_ = false;       ///< the index range has been established.
+  bool truncated_ = false;     ///< the producer overtook the scan at least once; sticky for the whole scan.
   u64 at_ = 0;                 ///< next absolute index to scan.
   u64 end_ = 0;                ///< one past the last absolute index to scan.
   double first_s_ = 0.0;       ///< stamp of `at_` when the scan began.