fix(app): show the sidebar toggle on plugin screens

Plugin screens rendered only their icon and title on the left of the header,
so on wide web and Android layouts there was no way to collapse the sidebar
from them, or to reopen it after it was closed elsewhere.

Fixes #6315

packages/app/e2e/browser/plugin-sidebar-items.spec.ts

@@ -241,6 +241,32 @@ test.describe("Plugin sidebar items", () => {
     });
   });
 
+  test("a plugin screen toggles the sidebar on a wide layout", async ({ page }) => {
+    await page.setViewportSize(WIDE);
+    await gotoWorkspace(page, workspaceId);
+    const row = headerRow(page, SHOWCASE_PLUGIN_ID, "deploys");
+    await expect(row).toBeVisible({ timeout: 30_000 });
+
+    await row.click();
+    await expect(page.getByText("Deploys screen body", { exact: true })).toBeVisible();
+    await visibleTestId(page, "menu-button").click();
+    await expect(row).not.toBeVisible();
+    await visibleTestId(page, "menu-button").click();
+    await expect(row).toBeVisible();
+    await closeScreen(page);
+
+    // With the sidebar closed elsewhere, the screen's own toggle is the way back to it.
+    await visibleTestId(page, "menu-button").click();
+    await expect(row).not.toBeVisible();
+    await page.keyboard.press("Control+k");
+    const panel = page.getByTestId("command-center-panel");
+    await panel.getByTestId("command-center-input").fill("Open deploys");
+    await panel.getByRole("button", { name: "Open deploys", exact: true }).click();
+    await expect(page.getByText("Deploys screen body", { exact: true })).toBeVisible();
+    await visibleTestId(page, "menu-button").click();
+    await expect(row).toBeVisible();
+  });
+
   test("a header row's shortcut hint presses the row", async ({ page }) => {
     await page.setViewportSize(WIDE);
     await gotoWorkspace(page, workspaceId);

packages/app/src/plugins/surface-screen.tsx

@@ -8,6 +8,7 @@ import { StyleSheet, withUnistyles } from "react-native-unistyles";
 import { HeaderIconBadge } from "@/components/headers/header-icon-badge";
 import { HeaderToggleButton } from "@/components/headers/header-toggle-button";
 import { CompactHeader } from "@/components/headers/compact-header";
+import { SidebarMenuToggle } from "@/components/headers/sidebar-menu-toggle";
 import { ScreenHeader } from "@/components/headers/screen-header";
 import { ScreenTitle } from "@/components/headers/screen-title";
 import { HostFilter } from "@/components/hosts/host-filter";
@@ -172,6 +173,7 @@ export function PluginSurfaceScreen() {
   const headerLeft = useMemo(
     () => (
       <>
+        <SidebarMenuToggle />
         {Icon ? (
           <HeaderIconBadge>
             <ThemedPluginHeaderIcon Icon={Icon} uniProps={mutedColorMapping} />