feat(ui): complete Plan 06-02 - Manus color tokens, thinking indicator, send button

- Apply Manus design tokens to index.css and tailwind.config.js
- Replace three-dot thinking indicator with pulsing blue dot + 'Thinking' text
- Change send button icon from ArrowUp to PaperPlaneRight
- Align message and input widths to 800px max

tauri-app/tailwind.config.js

@@ -20,6 +20,15 @@ export default {
         "c-danger":  "var(--danger)",
         "c-success": "var(--success)",
         "c-warn":    "var(--warning)",
+        // Manus design tokens
+        "manus-base":     "var(--manus-base)",
+        "manus-surface":  "var(--manus-surface)",
+        "manus-elevated": "var(--manus-elevated)",
+        "manus-hover":    "var(--manus-hover)",
+        "manus-tx":       "var(--manus-tx)",
+        "manus-tx2":      "var(--manus-tx2)",
+        "manus-tx3":      "var(--manus-tx3)",
+        "manus-blue":     "var(--manus-blue)",
       },
     },
   },