Expand workspace panel actions and keyboard navigation (#3685)

* fix(app): keep file navigation in place

Retargeting a File tab allocated a new tab identity, causing the tab track to unmount and remount during navigation. Preserve the identity for File-to-File changes while retaining new instances for cross-kind replacements.

* feat(app): expand workspace panel actions

Keep the Command Center aligned with workspace tab and pane primitives. Add explicit panel placement, focused open behavior, keyboard navigation for empty panes, and a Changes pill that toggles the visible Side panel without closing its tab.

packages/app/e2e/browser/composer-diff-stat.spec.ts

@@ -2,6 +2,7 @@ import { rm, writeFile } from "node:fs/promises";
 import path from "node:path";
 import { expect, test, type Page } from "../support/fixtures";
 import { openAgentRoute, seedMockAgentWorkspace } from "../support/helpers/mock-agent";
+import { openFilesPanel } from "../support/helpers/workspace-tabs";
 
 const APP_SETTINGS_KEY = "@paseo:app-settings";
 
@@ -37,7 +38,7 @@ async function seedChangedAgent(repoPrefix: string) {
   }
 }
 
-test("composer diff stat opens Changes in the preferred Side panel", async ({ page }) => {
+test("composer diff stat toggles Changes in the preferred Side panel", async ({ page }) => {
   const workspace = await seedChangedAgent("composer-diff-stat-side-");
 
   try {
@@ -58,6 +59,26 @@ test("composer diff stat opens Changes in the preferred Side panel", async ({ pa
       timeout: 30_000,
     });
     await expect(sidePanel.getByTestId("working-diff-panel")).toBeVisible({ timeout: 30_000 });
+
+    await test.step("switching from another Side panel view reveals Changes", async () => {
+      await openFilesPanel(page);
+      await expect(sidePanel.getByTestId("file-explorer-tree-scroll")).toBeVisible();
+
+      await pill.click();
+      await expect(sidePanel.getByTestId("working-diff-panel")).toBeVisible();
+    });
+
+    await test.step("clicking visible Changes hides the panel without closing its tab", async () => {
+      await pill.click();
+      await expect(sidePanel).toHaveCount(0);
+      await expect(page.getByTestId("workspace-tab-working_diff")).toHaveCount(1);
+    });
+
+    await test.step("clicking again restores Changes", async () => {
+      await pill.click();
+      await expect(sidePanel.getByTestId("workspace-tab-working_diff")).toBeVisible();
+      await expect(sidePanel.getByTestId("working-diff-panel")).toBeVisible();
+    });
   } finally {
     await workspace.cleanup();
   }

packages/app/e2e/browser/empty-pane-keyboard.spec.ts

@@ -0,0 +1,79 @@
+import { expect, type Locator, type Page } from "@playwright/test";
+import { test } from "../support/fixtures";
+import { runWorkspaceActionFromCommandCenter } from "../support/helpers/command-center-workspace-actions";
+import { gotoWorkspace } from "../support/helpers/launcher";
+import { seedWorkspace } from "../support/helpers/seed-client";
+import { waitForWorkspaceTabsVisible } from "../support/helpers/workspace-tabs";
+
+function visibleEmptyPane(page: Page): Locator {
+  return page.getByTestId("workspace-pane-empty-state").filter({ visible: true });
+}
+
+async function expectLauncherSelection(launcher: Locator, name: string): Promise<void> {
+  await expect(launcher.getByRole("button", { name })).toBeFocused();
+}
+
+async function openSidePanelWithKeyboard(page: Page): Promise<Locator> {
+  const modifier = process.platform === "darwin" ? "Meta" : "Control";
+  await page.keyboard.press(`${modifier}+E`);
+  const launcher = page
+    .getByTestId("workspace-side-panel")
+    .filter({ visible: true })
+    .getByTestId("workspace-pane-empty-state");
+  await expect(launcher).toBeVisible({ timeout: 30_000 });
+  return launcher;
+}
+
+test.describe("Empty pane keyboard launcher", () => {
+  test("Cmd+E focuses the launcher and Enter opens the selected view", async ({ page }) => {
+    const workspace = await seedWorkspace({ repoPrefix: "empty-pane-side-panel-keyboard-" });
+
+    try {
+      await gotoWorkspace(page, workspace.workspaceId);
+      await waitForWorkspaceTabsVisible(page);
+
+      const launcher = await openSidePanelWithKeyboard(page);
+      await expectLauncherSelection(launcher, "Changes");
+
+      await page.keyboard.press("ArrowDown");
+      await expectLauncherSelection(launcher, "Files");
+      await page.keyboard.press("Enter");
+
+      await expect(
+        page
+          .getByTestId("workspace-side-panel")
+          .filter({ visible: true })
+          .getByTestId("workspace-tab-files"),
+      ).toBeVisible({ timeout: 30_000 });
+    } finally {
+      await workspace.cleanup();
+    }
+  });
+
+  test("a new split pane focuses its launcher and wraps arrow navigation", async ({ page }) => {
+    const workspace = await seedWorkspace({ repoPrefix: "empty-pane-split-keyboard-" });
+
+    try {
+      await gotoWorkspace(page, workspace.workspaceId);
+      await waitForWorkspaceTabsVisible(page);
+      await runWorkspaceActionFromCommandCenter(page, "Split pane right");
+
+      const launcher = visibleEmptyPane(page);
+      await expect(launcher).toBeVisible({ timeout: 30_000 });
+      await expectLauncherSelection(launcher, "Changes");
+
+      await page.keyboard.press("ArrowUp");
+      await expectLauncherSelection(launcher, "Terminal");
+      await page.keyboard.press("ArrowDown");
+      await expectLauncherSelection(launcher, "Changes");
+      await page.keyboard.press("ArrowDown");
+      await page.keyboard.press("Enter");
+
+      await expect(page.getByTestId("workspace-tab-files").filter({ visible: true })).toBeVisible({
+        timeout: 30_000,
+      });
+    } finally {
+      await workspace.cleanup();
+    }
+  });
+});

packages/app/e2e/browser/file-transition.spec.ts

@@ -39,6 +39,12 @@ async function assertHeldFileTransition(
   finalText: string,
   gate: Awaited<ReturnType<typeof delayFileReadResponse>>,
 ) {
+  await page.evaluate(() => {
+    const originalChip = document.querySelector('[data-testid="workspace-tab-file_src/a.ts"]');
+    (
+      window as typeof window & { __fileTransitionOriginalChip?: Element | null }
+    ).__fileTransitionOriginalChip = originalChip;
+  });
   await page.evaluate((tabTestId) => {
     const timeline: Array<{ chip: boolean; loading: boolean; unavailable: boolean }> = [];
     const sample = () => {
@@ -69,6 +75,19 @@ async function assertHeldFileTransition(
   await expect(page.getByTestId("file-preview-unsupported")).toHaveCount(0);
   await expect(page.getByText("export const sourceA = true;")).toHaveCount(0);
 
+  const chipIdentity = await page.evaluate((tabTestId) => {
+    const windowWithOriginal = window as typeof window & {
+      __fileTransitionOriginalChip?: Element | null;
+    };
+    const originalChip = windowWithOriginal.__fileTransitionOriginalChip ?? null;
+    const currentChip = document.querySelector(`[data-testid="${tabTestId}"]`);
+    return {
+      originalStillConnected: originalChip?.isConnected ?? false,
+      sameNode: originalChip === currentChip,
+    };
+  }, `workspace-tab-file_${targetPath}`);
+  expect(chipIdentity).toEqual({ originalStillConnected: true, sameNode: true });
+
   const heldTimeline = await page.evaluate(
     () =>
       (