Add cancelled status for tasks

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/frontend/src/views/ProjectView.vue

@@ -108,7 +108,7 @@ const filteredDecisions = computed(() => {
 function taskStatusColor(s: string) {
   const m: Record<string, string> = {
     pending: 'gray', in_progress: 'blue', review: 'purple',
-    done: 'green', blocked: 'red', decomposed: 'yellow',
+    done: 'green', blocked: 'red', decomposed: 'yellow', cancelled: 'gray',
   }
   return m[s] || 'gray'
 }