feat(topbar): aggregated notification bell

Adds a Bell icon button to the topbar that sums chatUnreadCount +
queueCount and shows a single amber dot with the total. Click goes
to Chat if there are unread messages, otherwise to Approvals — the
scene most likely to be relevant. Per-tab badges on Approvals and
Chat tabs stay (they answer 'where' specifically), but operators who
just want 'do I have anything waiting' now get a single one-glance
signal in the topbar.

Title attr names the breakdown for accessibility. 31/31 vitest pass.

src/App.tsx

@@ -18,7 +18,7 @@ import Documents from "./scenes/Documents";
 import CommandBar from "./components/CommandBar";
 import Toaster from "./components/Toaster";
 import Console from "./components/Console";
-import { Cmd, Home, Layers, HistoryIcon, Pulse, Refresh, Branch, Cog, User, Sun, Moon, Bot } from "./components/icons";
+import { Cmd, Home, Layers, HistoryIcon, Pulse, Refresh, Branch, Cog, User, Sun, Moon, Bot, Bell } from "./components/icons";
 import { useBackendHealth } from "./lib/useBackendHealth";
 
 
@@ -216,6 +216,23 @@ export default function App() {
                 <Refresh size={12} /> Refresh
               </button>
             )}
+            <button
+              className={`link-btn notif-btn${(chatUnreadCount + queueCount) > 0 ? " has-notif" : ""}`}
+              onClick={() => setScene(chatUnreadCount > 0 ? "chat" : "approvals")}
+              title={
+                chatUnreadCount + queueCount === 0
+                  ? "Nothing waiting for you"
+                  : `${chatUnreadCount > 0 ? `${chatUnreadCount} unread message${chatUnreadCount === 1 ? "" : "s"}` : ""}${chatUnreadCount > 0 && queueCount > 0 ? " · " : ""}${queueCount > 0 ? `${queueCount} item${queueCount === 1 ? "" : "s"} in your queue` : ""}. Click to open ${chatUnreadCount > 0 ? "chat" : "approvals"}.`
+              }
+              aria-label={`Notifications: ${chatUnreadCount} unread, ${queueCount} queued`}
+            >
+              <Bell size={13} />
+              {(chatUnreadCount + queueCount) > 0 && (
+                <span className="notif-dot" aria-hidden>
+                  {(chatUnreadCount + queueCount) > 99 ? "99+" : chatUnreadCount + queueCount}
+                </span>
+              )}
+            </button>
             <button
               className={`link-btn${consoleOpen ? " is-on" : ""}`}
               onClick={() => setConsoleOpen(!consoleOpen)}

src/components/icons.tsx

@@ -41,3 +41,4 @@ export const Layers = (p: P) => <Svg {...p}><path d="M12 3l9 5-9 5-9-5zM3 13l9 5
 export const HistoryIcon = (p: P) => <Svg {...p}><path d="M3 12a9 9 0 1 0 3-6.7L3 8M3 3v5h5M12 7v5l3 2" /></Svg>;
 export const Home = (p: P) => <Svg {...p}><path d="M4 11l8-7 8 7v9h-5v-6h-6v6H4z" /></Svg>;
 export const ChevronRight = (p: P) => <Svg {...p}><path d="M9 18l6-6-6-6" /></Svg>;
+export const Bell = (p: P) => <Svg {...p}><path d="M6 8a6 6 0 0 1 12 0c0 7 3 7 3 9H3c0-2 3-2 3-9M10 21a2 2 0 0 0 4 0" /></Svg>;

src/index.css

@@ -2328,3 +2328,24 @@ select.studio-input { background: var(--bp-paper); }
   font-family: inherit;
 }
 .wizard-form-input:disabled { opacity: 0.7; }
+
+/* Aggregated topbar notification bell */
+.notif-btn { position: relative; display: inline-flex; align-items: center; gap: 4px; }
+.notif-btn.has-notif { color: var(--bp-amber, #d97a00); }
+.notif-dot {
+  position: absolute;
+  top: -3px;
+  right: -4px;
+  min-width: 14px;
+  height: 14px;
+  padding: 0 4px;
+  border-radius: 7px;
+  background: var(--bp-amber, #d97a00);
+  color: #fff;
+  font-family: var(--bp-mono, monospace);
+  font-size: 9px;
+  line-height: 14px;
+  text-align: center;
+  font-weight: 700;
+  pointer-events: none;
+}