Replace workspace reconnect banner with persistent agent panel toast

The workspace reconnect banner ignored safe-area insets on Android,
overlapping the system status bar. The agent panel already shows a
"Reconnecting..." toast on disconnect, so consolidate on that and drop
the banner entirely. Add persistent toast support (durationMs: null)
and dismiss the toast when the connection returns to online instead of
auto-dismissing after 2.2s.

packages/app/e2e/workspace-navigation-regression.spec.ts

@@ -157,7 +157,7 @@ test.describe("Workspace navigation regression", () => {
       });
 
       await daemonGate.drop();
-      await expect(page.getByTestId("workspace-reconnect-banner")).toBeVisible({
+      await expect(page.getByTestId("agent-reconnecting-toast")).toBeVisible({
         timeout: 30_000,
       });
       await expectWorkspaceHeader(page, {
@@ -172,7 +172,7 @@ test.describe("Workspace navigation regression", () => {
         label: "host reconnect",
       });
       daemonGate.restore();
-      await expect(page.getByTestId("workspace-reconnect-banner")).toHaveCount(0, {
+      await expect(page.getByTestId("agent-reconnecting-toast")).toHaveCount(0, {
         timeout: 30_000,
       });
       await monitorReconnect;