fix: power is RM5, not RM4 — the CW keying was the experiment

An FM carrier could not answer it: constant by definition, so nothing to
correlate. CW at 100 W did, because the keying itself varies the output:

  key down: RM4=25 RM5=207 RM6=13
  key up:   RM4=25 RM5=0   RM6=0

RM5 follows the RF envelope exactly — it IS the power meter. RM4 sits near 25
whether the key is down or up, so it is not measuring output at all, and reading
it as power is what showed 8 W on a 100 W transmission. The operator's hunch was
right and my first reading of the ramp was wrong: what I took for a needle
rising was RM4 drifting, not tracking.

Watts are now derived from that meter (207 = 100 W, measured) instead of the
power SETTING scaled by a percentage — the setting says what was asked for, the
meter says what left the radio.

The bars also hold their peak with a gentle decay. In CW the meters genuinely
read zero between elements, so following the raw value made them flash to nothing
several times a second; a needle has inertia, and this only ever holds a value
the radio really reported.

frontend/wailsjs/go/models.ts

@@ -1098,6 +1098,7 @@ export namespace cat {
 	    nr_level: number;
 	    narrow: boolean;
 	    swr: number;
+	    power_w: number;
 	    vox: boolean;
 	    key_speed: number;
 	    break_in: boolean;
@@ -1131,6 +1132,7 @@ export namespace cat {
 	        this.nr_level = source["nr_level"];
 	        this.narrow = source["narrow"];
 	        this.swr = source["swr"];
+	        this.power_w = source["power_w"];
 	        this.vox = source["vox"];
 	        this.key_speed = source["key_speed"];
 	        this.break_in = source["break_in"];