fix(sat): the Flex slices get their antenna, their sideband and their tone

Three things the tracker was leaving to chance on a FlexRadio, all reported from
a real pass.

ANTENNAS. Settings ▸ FlexRadio holds a per-band RX/TX antenna map, and it was
applied in exactly one place: the entry form, on a band change, to the active
slice. A pass never goes through that path — the tracker arms two slices itself.
So both were left on whatever the radio last used, and a station with
transverters (XVTA on 2 m, XVTB on 70 cm) heard nothing at all, having
configured precisely the thing being ignored. The two slices are on two
different bands, so they cannot share one setting: the downlink takes the
receive antenna for ITS band, the uplink the transmit antenna for its. Per
slice, not through sendSlice, which addresses whichever slice is active — during
a pass that is the downlink, so the uplink would never have been set.

SIDEBAND. satMode forced USB above 30 MHz on both sides. An inverting
transponder turns the passband over, so lower sideband up comes back as upper
sideband down: FO-29, RS-44 and AO-73 were being worked with the operator's own
audio going through upside down. The tracker now decides both sidebands from the
transponder's inverting flag and passes them separately; a bare "SSB" still
means USB, so nothing else changes.

CTCSS. Nothing set it, on any bird. The frequency plan has carried the tone all
along — 67.0 on SO-50 and AO-91, 141.3 on PO-101 — and an FM repeater does not
answer without it, which is indistinguishable from a satellite that is not
there. It goes on the uplink slice, value before mode so the radio cannot
transmit the previous tone in the gap between two commands.

Written against the SmartSDR slice API and UNTESTED on hardware.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

app_sat_track_test.go

@@ -106,3 +106,32 @@ func (c *countingRotator) Point(az, el float64) error {
 }
 func (c *countingRotator) Heading() (float64, float64, bool, error) { return 0, 0, false, nil }
 func (c *countingRotator) Close()                                   {}
+
+// Which sideband goes on each slice.
+//
+// An inverting transponder turns the passband over, so a signal transmitted on
+// lower sideband comes back on upper. Setting USB at both ends put the
+// operator's own audio through upside down — unreadable at the far end, and on
+// FO-29, RS-44 and AO-73 that is every contact attempted.
+func TestSatSidebands(t *testing.T) {
+	cases := []struct {
+		name           string
+		tp             sat.Transponder
+		wantDown, want string
+	}{
+		{"inverting linear: LSB up, USB down",
+			sat.Transponder{Mode: "SSB", Inverting: true}, "USB", "LSB"},
+		{"non-inverting linear: USB both ways",
+			sat.Transponder{Mode: "SSB"}, "USB", "USB"},
+		// A tone is transmitted and received in FM whichever way the passband
+		// runs, and CW is CW.
+		{"FM is FM both ways", sat.Transponder{Mode: "FM"}, "FM", "FM"},
+		{"CW ignores inversion", sat.Transponder{Mode: "CW", Inverting: true}, "CW", "CW"},
+	}
+	for _, c := range cases {
+		down, up := satSidebands(c.tp)
+		if down != c.wantDown || up != c.want {
+			t.Errorf("%s: got %s/%s, want %s/%s", c.name, down, up, c.wantDown, c.want)
+		}
+	}
+}