fix: the marks are read a frame after the jump, so a placed count is read from the window it is on

The plan's Task 8 named the search probe as its test but never extended it, and leaned on the
exit dump instead -- which stops the tick from Live, where no hit is in view, so it reads
placed=0 for a correct implementation and a broken one alike.

src/ui.cpp

@@ -9085,6 +9085,36 @@ gboolean condition_probe(gpointer user) {
 /// prevent. It then steps to a hit and reports the pinned axis against it.
 double g_search_t0 = 0.0;
 
+/// Reports the marks a *frame* after the jump, because that is the only moment they can be read
+/// honestly: `search_jump()` publishes a pause view, but the axis it is pinned against and the
+/// `view_range()` that `place_search_marks()` filters by are both settled by the frame tick, not
+/// by the publish. Reading `search_marks_placed()` in the same callback as the jump would quote
+/// the window the scope was on *before* it moved.
+///
+/// This cannot be read from the exit dump instead. The exit probe stops the tick from `Live`,
+/// where the newest window holds no hit at all, so a dump reading is `placed=0` whatever the
+/// marks did -- true of a correct implementation and of a broken one alike. The dump's own line
+/// asserts the thing that does survive going live: that the new cursor pool is unselectable.
+gboolean search_probe_marks(gpointer user) {
+  App* a = static_cast<App*>(user);
+  if (a->window == nullptr) return G_SOURCE_REMOVE;
+  const plot::Range view = a->rows->view_range();
+  std::size_t in_view = 0;
+  const double s0 = a->model->stream_at_x0();
+  for (const double h : a->search.hits()) {
+    const double x = h - s0;
+    if (x >= view.min && x <= view.max) ++in_view;
+  }
+  std::fprintf(stderr,
+               "[search-probe] marks placed=%d of %zu in view (%zu found) locked=%d mode=%d "
+               "axis=[%.4f..%.4f]\n",
+               a->rows->search_marks_placed(), in_view, a->search.hits().size(),
+               a->rows->readouts_locked() ? 1 : 0, int(a->model->display_mode()), view.min,
+               view.max);
+  std::fflush(stderr);
+  return G_SOURCE_REMOVE;
+}
+
 gboolean search_probe_report(gpointer user) {
   App* a = static_cast<App*>(user);
   if (a->window == nullptr) return G_SOURCE_REMOVE;
@@ -9123,6 +9153,7 @@ gboolean search_probe_report(gpointer user) {
                  "[search-probe] jumped to hit 0 t=%.6f mode=%d axis=[%.4f..%.4f] pos=%d\n",
                  a->search.hits()[0], int(a->model->display_mode()), view.min, view.max,
                  a->search.cursor() + 1);
+    g_timeout_add(250, search_probe_marks, a);
   }
   std::fflush(stderr);
   return G_SOURCE_REMOVE;