Add streaming status UX and model load state indicator

Streaming status transparency:
- generation_task.py emits 'status' SSE events at each pipeline stage:
  "Analyzing your request..." before intent classification, tool label
  before each tool execution, "Generating/Composing response..." before
  each LLM streaming round
- chat.ts adds streamingStatus ref; cleared on first chunk or done/error;
  includes fast 5s poll loop after warmModel() until model shows as loaded
- ChatView.vue shows pulsing dot + italic status label above content area;
  falls back to blinking cursor once content arrives
- HomeView.vue shows status label in dashboard panel instead of '...'

Model load state indicator:
- /api/chat/status now queries /api/tags and /api/ps in parallel to
  distinguish installed-but-cold vs loaded-in-VRAM model states
- New model status values: 'not_found' | 'cold' | 'loaded' (was 'ready')
- chatReady true for both 'cold' and 'loaded' (cold models still work)
- AppHeader shows 5 states: gray pulse (checking), red (Ollama down),
  orange (not installed), yellow pulse (cold), green (loaded)
- Inline short label ("Cold", "Ready", "Offline", etc.) visible without
  hovering; detailed tooltip on hover

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

frontend/src/components/AppHeader.vue

@@ -14,18 +14,31 @@ const chatStore = useChatStore();
 const router = useRouter();
 const mobileMenuOpen = ref(false);
 
+const statusShortLabel = computed(() => {
+  if (chatStore.ollamaStatus === "unavailable") return "Offline";
+  if (chatStore.ollamaStatus === "checking") return "Checking";
+  if (chatStore.modelStatus === "not_found") return "No model";
+  if (chatStore.modelStatus === "cold") return "Cold";
+  if (chatStore.modelStatus === "loaded") return "Ready";
+  return "Checking";
+});
+
 const statusLabel = computed(() => {
   if (chatStore.ollamaStatus === "unavailable") return "Ollama unavailable";
-  if (chatStore.modelStatus === "not_found") return "Model downloading...";
-  if (chatStore.chatReady) return "Connected";
+  if (chatStore.ollamaStatus === "checking") return "Checking...";
+  if (chatStore.modelStatus === "not_found") return "Model not installed";
+  if (chatStore.modelStatus === "cold") return "Model cold — first response may be slow";
+  if (chatStore.modelStatus === "loaded") return "Model loaded · ready";
   return "Checking...";
 });
 
 const statusClass = computed(() => {
   if (chatStore.ollamaStatus === "unavailable") return "status-red";
-  if (chatStore.modelStatus === "not_found") return "status-yellow";
-  if (chatStore.chatReady) return "status-green";
-  return "status-yellow";
+  if (chatStore.ollamaStatus === "checking") return "status-gray";
+  if (chatStore.modelStatus === "not_found") return "status-orange";
+  if (chatStore.modelStatus === "cold") return "status-yellow";
+  if (chatStore.modelStatus === "loaded") return "status-green";
+  return "status-gray";
 });
 
 function toggleMobileMenu() {
@@ -67,6 +80,7 @@ router.afterEach(() => {
         <router-link v-if="authStore.isAdmin" to="/admin/logs" class="nav-link">Logs</router-link>
         <span class="status-indicator" :class="statusClass" :title="statusLabel">
           <span class="status-dot"></span>
+          <span class="status-text">{{ statusShortLabel }}</span>
         </span>
         <button class="btn-shortcuts" @click="toggleShortcuts" title="Keyboard shortcuts (?)">
           ?
@@ -147,7 +161,9 @@ router.afterEach(() => {
 .status-indicator {
   display: flex;
   align-items: center;
+  gap: 0.3rem;
   margin-left: 0.5rem;
+  cursor: default;
 }
 .status-dot {
   width: 8px;
@@ -155,19 +171,31 @@ router.afterEach(() => {
   border-radius: 50%;
   flex-shrink: 0;
 }
+.status-text {
+  font-size: 0.75rem;
+  font-weight: 500;
+  color: var(--color-text-muted);
+}
 .status-green .status-dot {
-  background: var(--color-success);
+  background: var(--color-success, #2ecc71);
 }
 .status-yellow .status-dot {
-  background: var(--color-warning);
+  background: var(--color-warning, #f59e0b);
   animation: pulse-dot 2s infinite;
 }
+.status-orange .status-dot {
+  background: #f97316;
+}
 .status-red .status-dot {
-  background: var(--color-danger);
+  background: var(--color-danger, #e74c3c);
+}
+.status-gray .status-dot {
+  background: var(--color-text-muted);
+  animation: pulse-dot 2s infinite;
 }
 @keyframes pulse-dot {
   0%, 100% { opacity: 1; }
-  50% { opacity: 0.4; }
+  50% { opacity: 0.3; }
 }
 .btn-shortcuts {
   background: none;