feat(dashboard): add working indicator for active sessions

Visual feedback when an agent is actively processing:

1. **Spinner on status dots** (SessionCard.js, Modal.js)
   - Status dot gets a spinning ring animation when session is active/starting
   - Uses CSS border trick with transparent borders except top

2. **Working indicator in chat** (ChatMessages.js, Modal.js)
   - Shows at bottom of conversation when agent is working
   - Bouncing dots animation ("...") next to "Agent is working" text
   - Only visible for active/starting statuses

3. **CSS animations** (styles.css)
   - spin-ring: 0.8s rotation for the status dot border
   - bounce-dot: staggered vertical bounce for the working dots

4. **Status metadata** (status.js)
   - Added `spinning: true` flag for active and starting statuses
   - Used by components to conditionally render spinner elements

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dashboard/styles.css

@@ -67,6 +67,36 @@ body {
   animation: pulse-attention 2s ease-in-out infinite;
 }
 
+/* Active session spinner */
+@keyframes spin-ring {
+  to { transform: rotate(360deg); }
+}
+
+.spinner-dot {
+  position: relative;
+  display: inline-block;
+}
+
+.spinner-dot::after {
+  content: '';
+  position: absolute;
+  inset: -2px;
+  border-radius: 50%;
+  border: 1.5px solid transparent;
+  border-top-color: currentColor;
+  animation: spin-ring 0.8s linear infinite;
+}
+
+/* Working indicator at bottom of chat */
+@keyframes bounce-dot {
+  0%, 80%, 100% { transform: translateY(0); }
+  40% { transform: translateY(-4px); }
+}
+
+.working-dots span:nth-child(1) { animation: bounce-dot 1.2s ease-in-out infinite; }
+.working-dots span:nth-child(2) { animation: bounce-dot 1.2s ease-in-out 0.15s infinite; }
+.working-dots span:nth-child(3) { animation: bounce-dot 1.2s ease-in-out 0.3s infinite; }
+
 /* Glass panel effect */
 .glass-panel {
   backdrop-filter: blur(10px);