fix: restore +New button (desktop only) and fix E2E tests (#155)

Fixes E2E tests that were broken by the code viewer PR (#154).

### Problem
The code viewer PR removed the `+ New` button and hid session name +
status dot on mobile, which broke E2E tests:
- Tests clicking `[data-testid="tab-new-btn"]` couldn't find it
- Mobile tests checking `[data-testid="status-dot"].connected` couldn't
find it
- Mobile test creating sessions via `button[title="New tab"]` failed

### Fix
- **Restored `+ New` button** with `desktopOnly` class — visible on
desktop (where E2E runs at 1280x720), hidden on mobile
- **Keep status dot visible** on all viewports — it's small and useful,
and mobile E2E tests check it
- **Session name hidden** on mobile only (not on desktop)
- **Fixed keybar E2E test**: mobile session-creation test now uses side
panel "`+ New Session`" button instead of the top bar button

### Verification
All 85 E2E tests pass locally:
```
85 passed (1.7m)
```

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dorlugasigal

src/frontend/src/components/TerminalApp/TerminalApp.module.css

@@ -169,7 +169,6 @@
     display: flex !important;
   }
   .sessionName,
-  .statusDot,
   .statusText {
     display: none;
   }

src/frontend/src/components/TerminalApp/TerminalApp.tsx

@@ -40,6 +40,7 @@ export function TerminalApp() {
   const closeCommandPalette = useUIStore((s) => s.closeCommandPalette);
   const closeSearchBar = useUIStore((s) => s.closeSearchBar);
   const openSidePanel = useUIStore((s) => s.openSidePanel);
+  const openNewSessionModal = useUIStore((s) => s.openNewSessionModal);
   const fontSize = useUIStore((s) => s.fontSize);
   const showDownload = useUIStore((s) => s.downloadModalOpen);
   const closeDownloadModal = useUIStore((s) => s.closeDownloadModal);
@@ -373,6 +374,31 @@ export function TerminalApp() {
         <TabBar inline />
 
         <div className={styles.right}>
+          <button
+            className={`${styles.barBtn} ${styles.barBtnWithLabel} ${styles.desktopOnly}`}
+            data-testid="tab-new-btn"
+            onClick={() => {
+              if (document.activeElement instanceof HTMLElement) document.activeElement.blur();
+              openNewSessionModal();
+            }}
+            onTouchStart={(e) => e.stopPropagation()}
+            aria-label="New tab"
+            title="New tab"
+          >
+            <svg
+              width="14"
+              height="14"
+              viewBox="0 0 24 24"
+              fill="none"
+              stroke="currentColor"
+              strokeWidth="2.5"
+              strokeLinecap="round"
+            >
+              <line x1="12" y1="5" x2="12" y2="19" />
+              <line x1="5" y1="12" x2="19" y2="12" />
+            </svg>
+            <span className={styles.btnLabel}>New</span>
+          </button>
           <button
             className={styles.barBtn}
             onClick={toggleCommandPalette}

test/e2e-keybar.test.js

@@ -741,8 +741,10 @@ test.describe('Top Bar — Side Panel (mobile viewport)', () => {
     await runCommand(page, `echo ${marker1}`);
     await waitForTerminalOutput(page, marker1);
 
-    // Create a second session via modal
-    await page.locator('button[title="New tab"]').click();
+    // Create a second session via side panel (mobile — top bar + New is hidden)
+    await page.locator('[aria-label="Toggle panel"]').click();
+    await expect(page.locator('[data-testid="side-panel"]')).toBeVisible();
+    await page.getByRole('button', { name: '+ New Session' }).click();
     await expect(page.locator('[data-testid="new-session-modal"]')).toBeVisible();
     await page.locator('[data-testid="ns-name"]').fill('Second');
     await page.locator('[data-testid="ns-create"]').click();