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

docs/claude/probe-readings.md

@@ -1165,14 +1165,15 @@ through one row type, for the reason in `invariants-gtk-and-chrome.md`. The form
 ## `trigger panel:`
 
 ```
-[udpscope]   trigger panel: boxes=13 controls_inside=13/13 search_widgets=4/4 search_inside=4/4
+[udpscope]   trigger panel: boxes=15 controls_inside=15/15 search_widgets=4/4 search_inside=4/4
 ```
 
 The trigger panel's frame, read from the window: `boxes` is the row boxes the `.ui` holds, `controls_inside`
-counts the thirteen controls the code built and then appended into those rows, `search_widgets` is the four
+counts the fifteen controls the code built and then appended into those rows -- the last two being the
+noise band and the HF reject, whose rows arrived with the noise-rejection work, `search_widgets` is the four
 search buttons having resolved by id, and `search_inside` is those four being inside the block the expander
 opens onto. A control built and never placed -- an id that drifted between the file and the code -- reads as
-`controls_inside` below 13 while every other line still looks right, which is the panel that has a field
+`controls_inside` below 15 while every other line still looks right, which is the panel that has a field
 missing.
 
 The search walk starts at `gtk_expander_get_child()`, not at the panel: an expander's child is not in the