Put the bands down the side of the entry window

N1MM has two columns of band buttons beside its entry window, CW in one and
phone in the other, with the band the radio is on marked. This has the same.

A button does not jump to the band edge every time: BandMemory keeps the
frequency the operator was last on for each band and mode, so leaving 20 metres
at 14032 and coming back lands on 14032. The first visit to a band starts where
that part of it starts, which the band plan says — the bottom edge for CW, the
CW-to-phone boundary for phone — and a band the plan says nothing about starts
at its bottom edge.

Phone picks the sideband the band calls for, so 40 metres is lower sideband and
20 is upper.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -173,6 +173,13 @@ in again while you are running, and `EsmSendsCorrectedCall` sends the call again
 in front of the last message when you have corrected it — copy `SM3AB`, fix it
 to `SM3ABC`, and the key sends `SM3ABC TU DL1ABC`.
 
+### The band buttons
+
+Down the left of the entry window are the bands, CW in one column and phone in
+the other, as N1MM has them. A button puts the radio where you left that band
+and mode, or at the start of that part of the band the first time. The button
+for where the radio is now is marked.
+
 ### Where the other station is
 
 Under the entry window is the line N1MM writes there: the beam heading, the