Mirror a radio from another computer's broadcast data

Listen for Radio broadcast data from another Nonemm or N1MM computer and
record its frequency, mode and split as this computer's own radio. No
radio is controlled. The settings are in the Configure Radios dialog.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/unfinished.md

@@ -761,6 +761,15 @@ detail than N1MM:
 - **Contacts, All Computers.** Only logged contacts are passed on, not edits or
   deletes.
 
+## Radio mirror
+
+Config ▸ Radio Mirror copies the frequency, mode and split of a radio on another
+computer, for a station whose radio port is used up. The listener applies
+`RadioInfo` to the entry position of one local radio and commands no radio. Nothing is checked against a real N1MM or two
+real stations; the test sends our own message over loopback. A mode name other
+than `CW-R` and `FSK` that this program has no mode for leaves the mode
+unchanged. `IsTransmitting` is read but not used.
+
 ## Known rough edges
 
 **The band plan covers 160M to 2M only.** 60M and everything above 2M get no