fix: send "vessels" to the ships layer in voice

Voice hears audio directly, and "vessels" is easily heard as "visuals",
which the instructions route to visual styles, so asking for vessels turned
on other layers or a CRT style. The instructions now say a vessels request
without a style name means the ships layer, and a style needs its name.

src/tooling/localServices.test.mjs

@@ -485,3 +485,9 @@ test('the voice instructions name only tools the voice session offers', async ()
   );
   assert.deepEqual(missing, []);
 });
+
+test('the voice instructions send vessels, however heard, to the ships layer', () => {
+  const text = realtimeInstructions();
+  assert.match(text, /"vessels" is easily heard as "visuals"/);
+  assert.match(text, /set_layer_visibility\{layerId:"ais-live-vessels"\}/);
+});