ui: the trigger panel offers a noise band and an HF reject

Two label-only rows in trigger-panel.ui (band_row, hf_row, after holdoff_row and before
mode_row) and the two spins the code appends into them: the band on the level spins' scale
in signal units, the HF reject at 0-1e7 Hz with 0 off. Both are published with the other
fields -- read before the model lock is taken, assigned inside it -- and both join the
value-changed loop, so editing either republishes the condition.

The rows are shown per type: the band for every type but Dropout, which is an absence a
band cannot describe, and the HF reject for all of them, since it sits before every
comparison. `sync_trigger_rows()` resolves a row as its spin's parent rather than keeping a
second handle to it: the row comes from the file and holds one child.

The exit dump counts the panel's controls, so it reads controls_inside=15/15 now -- and the
probe confirms it, along with both search readings and no Gtk-CRITICAL:

    [udpscope] trigger panel: boxes=15 controls_inside=15/15 search_widgets=4/4 search_inside=4/4

src/ui.cpp

@@ -5812,7 +5812,7 @@ int run_ui(int argc, char** argv, const Config& cfg, ScopeModel& model, Acquisit
           (app.search_run_button != nullptr) + (app.search_cancel_button != nullptr) +
           (app.search_prev_button != nullptr) + (app.search_next_button != nullptr);
       std::printf(
-          "[udpscope]   trigger panel: boxes=%d controls_inside=%d/13 search_widgets=%d/4 "
+          "[udpscope]   trigger panel: boxes=%d controls_inside=%d/15 search_widgets=%d/4 "
           "search_inside=%d/4\n",
                   boxes,
                   inside(app.trigger_signal_drop, app.trigger_panel) +
@@ -5827,6 +5827,8 @@ int run_ui(int argc, char** argv, const Config& cfg, ScopeModel& model, Acquisit
                       inside(app.trigger_level_spin, app.trigger_panel) +
                       inside(app.trigger_pre_spin, app.trigger_panel) +
                       inside(app.trigger_holdoff_spin, app.trigger_panel) +
+                      inside(app.trigger_band_spin, app.trigger_panel) +
+                      inside(app.trigger_hf_spin, app.trigger_panel) +
                       inside(app.events_record_switch, app.trigger_panel),
                   search_present,
                   inside(app.search_run_button, search_root) + inside(app.search_cancel_button, search_root) +