Add N1MM's Mark and Store buttons

Both put something on our own bandmap and nothing on the cluster, which is
what separates them from Spot It.

Mark, Alt+M, leaves a mark where the radio is to say the frequency is busy.
The label is N1MM's, Busy@ and the time. It is not a station, so Spot carries
IsStation: nothing judges it, the check window does not offer it as a call,
available mults and Qs leaves it out, space does not take it into the callsign
box, and the bandmap paints it like a station already worked, which is how
N1MM marks it. The station count under the bandmap counts stations.

Store, Alt+O, puts the call being typed on the bandmap at this frequency so it
can be worked later. N1MM writes "Local spot" in the comment and this does the
same.

The action row now holds the eight buttons N1MM has, in N1MM's order and at
N1MM's widths: 23 per cent to Esc: Stop and 11 to each of the rest.

Left out of Store: N1MM also adds the call to what the check window's Master
column offers for the rest of the session. The call is on the bandmap, which
the check window already reads, so it is offered either way.

Driven under Xvfb: Alt+M leaving BUSY@22:32:27 on 14000, Alt+O storing
SP9XYZ there, and both drawn on the bandmap in the worked colour.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RoGtneMQaz4M9w7Kk49AVD

README.md

@@ -247,13 +247,21 @@ them, between the entry boxes and the bearing line, which is where N1MM puts
 them. Each row fills the width, and the first button of the action row takes the
 23 per cent N1MM gives it.
 
-The action row is N1MM's: Esc: Stop, Wipe, Log It, Edit, Spot It and QRZ, each
-doing what its key does. QRZ opens the callsign's page in a browser.
+The action row is N1MM's: Esc: Stop, Wipe, Log It, Edit, Mark, Store, Spot It
+and QRZ, each doing what its key does. QRZ opens the callsign's page in a
+browser.
 
-N1MM's other two buttons are not there. Both put something on your own bandmap
-rather than on the cluster: Mark leaves a `Busy@` marker at the frequency you
-are on, which needs a bandmap entry that is not a station, and Store puts the
-call being typed there so you can come back to it.
+Mark and Store put something on your own bandmap rather than on the cluster, and
+have N1MM's keys:
+
+- **Mark**, Alt+M, leaves a `Busy@` mark where the radio is, so you know not to
+  come back to that frequency. It is not a station: nothing judges it, it is
+  never offered as a call to work, space does not take it into the callsign box,
+  and the bandmap paints it like a station already worked, which is how N1MM
+  marks it.
+- **Store**, Alt+O, puts the call being typed on the bandmap at this frequency
+  so it can be worked later. Spot It sends the same call to the cluster; Store
+  keeps it here.
 
 The title bar says what N1MM's says: the frequency, the mode, whether the
 frequency came from a radio or was typed, and which radio the window belongs to