fix(app): seed changes tab in explorer pane even when setup tab occupies it

The explorer companion pane retention commit (de9e85862) auto-opens the
setup progress tab into the hidden explorer pane. toggleWorkspaceExplorerPane
only seeded the working_diff (Changes) tab when the pane was completely
empty, so once the setup tab landed there, clicking the explorer toggle
could never surface Changes/Files again via that pane's default tab.

Also fixes two e2e testid locators (workspace-new-tab-menu-trigger) and
one unit test assertion (browser automation handler) that assumed a bare
pane root, which predates that same explorer-pane-retention change: the
workspace root is now always a group with a hidden companion pane, so
unscoped locators/assertions must target the visible/named pane.

packages/app/e2e/browser/terminal-stuck-size.spec.ts

@@ -56,7 +56,10 @@ async function readRenderedTerminalSize(page: Page): Promise<RenderedTerminalSiz
 }
 
 async function createTerminalViaMenu(page: Page): Promise<void> {
-  await page.getByTestId("workspace-new-tab-menu-trigger").click();
+  // Workspaces always render a hidden explorer companion pane alongside the
+  // main pane, so an unscoped testid locator matches both; scope to the
+  // visible one.
+  await page.getByTestId("workspace-new-tab-menu-trigger").filter({ visible: true }).click();
   await page.getByTestId("workspace-new-tab-menu-terminal").click();
 }
 
@@ -124,7 +127,9 @@ test.describe("terminal PTY size claim under lost window focus", () => {
     await page.setViewportSize({ width: 1280, height: 900 });
 
     await page.goto(buildHostWorkspaceRoute(getServerId(), harness.workspaceId));
-    await expect(page.getByTestId("workspace-new-tab-menu-trigger")).toBeVisible({
+    await expect(
+      page.getByTestId("workspace-new-tab-menu-trigger").filter({ visible: true }),
+    ).toBeVisible({
       timeout: 30_000,
     });
 

packages/app/src/desktop/browser/automation/handler.test.ts

@@ -4,6 +4,7 @@ import { createJSONStorage, type StateStorage } from "zustand/middleware";
 import { mountBrowserAutomationHandler } from "./handler";
 import type { DesktopHostBridge } from "@/desktop/host";
 import { useBrowserStore } from "@/desktop/browser/store";
+import { findPaneById } from "@/stores/workspace-layout-actions";
 import { useWorkspaceLayoutStore } from "@/stores/workspace-layout-store";
 import { buildWorkspaceTabPersistenceKey } from "@/workspace-tabs/model";
 
@@ -306,11 +307,15 @@ describe("mountBrowserAutomationHandler", () => {
         target: { kind: "browser", browserId: result.browserId },
       }),
     ]);
-    expect(layout?.root).toEqual(
-      expect.objectContaining({
-        kind: "pane",
-        pane: expect.objectContaining({ focusedTabId: previousFocusedTabId }),
-      }),
+    // Workspaces keep a stable hidden explorer companion pane at the root
+    // (see "retain workspace explorer pane"), so the root is a group and the
+    // draft/browser tabs land in the "main" pane, not at the root directly.
+    if (!layout) {
+      throw new Error("Expected workspace layout");
+    }
+    expect(layout.root.kind).toBe("group");
+    expect(findPaneById(layout.root, "main")).toEqual(
+      expect.objectContaining({ focusedTabId: previousFocusedTabId }),
     );
     expect(openedTabs[0]?.tabId).not.toBe(previousFocusedTabId);
     expect(browser.browser.activeWorkspaceBrowsers).toEqual([]);

packages/app/src/screens/workspace/workspace-screen.tsx

@@ -1404,7 +1404,15 @@ function toggleWorkspaceExplorerPane(input: ToggleWorkspaceExplorerPaneInput): v
       store.hidePane(input.persistenceKey, explorerPane.id);
       return;
     }
-    if (explorerPane.tabIds.length === 0) {
+    // The companion pane can already hold an unrelated tab (the setup
+    // progress tab auto-opens here) before the user ever toggles it, so
+    // "empty" is the wrong signal for "needs a Changes tab seeded". Check
+    // for the working_diff tab specifically.
+    const layoutTabs = collectAllTabs(layout.root);
+    const hasWorkingDiffTab = explorerPane.tabIds.some(
+      (tabId) => layoutTabs.find((tab) => tab.tabId === tabId)?.target.kind === "working_diff",
+    );
+    if (!hasWorkingDiffTab) {
       const tabId = parentTabId
         ? store.openChildTabFocused(input.persistenceKey, { kind: "working_diff" }, parentTabId)
         : store.openTabFocused(input.persistenceKey, { kind: "working_diff" });