feat(web): no_recipient toast copy arm (#18)

buildCallUndeliverableToast renders "{peerLabel} couldn't ring anyone."
for the single-failure terminal case; multi-failure + non-terminal paths
fall through to existing lines (which already fold the new reason in by
peer label). TDD — four new assertions.

packages/web/src/utils/callUndeliverableToast.ts

@@ -76,6 +76,8 @@ export function buildCallUndeliverableToast(
       return `Could not reach ${label}. Try again in a moment.`;
     case 'livekit_unavailable':
       return 'Voice is not configured on this instance.';
+    case 'no_recipient':
+      return `${label} couldn't ring anyone.`;
     default:
       return `Call to ${label} could not be placed.`;
   }