add telemetry messages: rx link quality, battery percentage, flight mode, relative altitude

app/test/transport/msp/msp_telemetry_codec_test.dart

@@ -94,4 +94,48 @@ void main() {
       expect(parseMspNavStatusActiveWaypoint(navStatusPayload(5)), 5);
     });
   });
+
+  group('parseMspNavMode/MspNavMode.formatted', () {
+    Uint8List navStatusPayload(int mode, int state) {
+      return Uint8List.fromList([mode, state, 0, 0, 0, 0, 0]);
+    }
+
+    test('mode 0 (None) ohne state', () {
+      final nav = parseMspNavMode(navStatusPayload(0, 0));
+      expect(nav.mode, 0);
+      expect(nav.state, 0);
+      expect(nav.formatted, 'Idle');
+    });
+
+    test('mode 3 (Nav/Waypoint) + state 5 (WP_ENROUTE)', () {
+      final nav = parseMspNavMode(navStatusPayload(3, 5));
+      expect(nav.formatted, 'Waypoint mission (en route to WP)');
+    });
+
+    test('mode 2 (RTH) + state 15 (RTH_CLIMB)', () {
+      final nav = parseMspNavMode(navStatusPayload(2, 15));
+      expect(nav.formatted, 'Return to home (climbing)');
+    });
+
+    test('unbekannter mode faellt auf Nummer zurueck', () {
+      final nav = parseMspNavMode(navStatusPayload(7, 0));
+      expect(nav.formatted, 'Unknown (7)');
+    });
+  });
+
+  group('parseMspInavAnalogBatteryPercent', () {
+    test('liest Batterie-Prozent an Offset 21', () {
+      final payload = Uint8List(24);
+      payload[21] = 42;
+      expect(parseMspInavAnalogBatteryPercent(payload), 42);
+    });
+  });
+
+  group('parseMspLinkQuality', () {
+    test('liest Linkqualitaet an Offset 1', () {
+      final payload = Uint8List(3);
+      payload[1] = 87;
+      expect(parseMspLinkQuality(payload), 87);
+    });
+  });
 }