fix(ui): stop Escape from stranding the keyboard after closing an overlay

Both the Command Palette and the Session Manager call `search.focus()` on
open, and both closed by removing the `active` class and nothing else. Hiding
a focused input does not hand focus back to anyone — the browser drops it on
`<body>` — so after Escape closed the overlay every keystroke went nowhere and
the user had to click the terminal before they could type again.

Measured in headless chromium against a real shell session, one overlay at a
time:

  overlay            activeElement after Esc   can type afterwards
  App Settings       XTERM                     yes
  Session Options    XTERM                     yes
  Token Stats        XTERM                     yes
  Monitor Panel      XTERM                     yes
  Session Manager    BODY                      no    <- fixed here
  Command Palette    BODY                      no    <- fixed here

The four that worked did so because they use `FocusTrap`, whose `deactivate()`
restores focus to whatever held it before. These two never got one. Every close
path has the same hole — Escape, the close method, picking an item — so the
restore lives in the close functions rather than in the global Escape chain.

Deliberately only the save/restore half of `FocusTrap`, not the whole thing:
`FocusTrap.activate()` moves focus to the first focusable element, which in
neither overlay is the search box, so adopting it wholesale would trade "type a
filter the moment it opens" for "focus survives the close" — and the former is
the reason Cmd+K exists. The terminal fallback is gated on there being an
active session: an overlay opened from the welcome screen has no terminal to
return to, and focusing one on a phone summons the on-screen keyboard over a
screen with no input on it.

The five new cases were checked against the unfixed code first: four of them
fail without this change.

test/command-palette-ui.test.ts

@@ -480,6 +480,84 @@ describe('Session Manager unified list', () => {
   });
 });
 
+describe('overlay focus restoration (Escape must not strand the keyboard)', () => {
+  /**
+   * Both overlays focus their search box on open. Closing them used to leave
+   * focus on <body>, so after Escape every keystroke went nowhere until the
+   * user clicked the terminal — measured in a real browser against a shell
+   * session: activeElement BODY, zero onData for anything typed afterwards.
+   */
+  function focusHarness() {
+    const terminalTextarea = { focus: vi.fn(), isConnected: true };
+    const priorElement = { focus: vi.fn(), isConnected: true, tagName: 'TEXTAREA' };
+    const body = { tagName: 'BODY' };
+    let active: any = priorElement;
+    const { app, elements } = loadPaletteHarness({
+      document: {
+        getElementById: (id: string) => (globalThis as any).__els?.[id] ?? null,
+        get activeElement() {
+          return active;
+        },
+        body,
+      },
+    });
+    (globalThis as any).__els = elements;
+    app.terminal = { focus: terminalTextarea.focus };
+    app.activeSessionId = 'sess-beta';
+    // The overlay's own focus() is what moves focus in a real browser; the
+    // fake document needs the same transition or the test proves nothing.
+    elements.commandPaletteSearch.focus = vi.fn(() => {
+      active = elements.commandPaletteSearch;
+    });
+    return { app, elements, priorElement, terminalTextarea, body, setActive: (v: any) => (active = v) };
+  }
+
+  it('returns focus to whatever had it when the command palette closes', () => {
+    const { app, priorElement } = focusHarness();
+    app.openCommandPalette();
+    expect(priorElement.focus).not.toHaveBeenCalled();
+    app.closeCommandPalette();
+    expect(priorElement.focus).toHaveBeenCalledTimes(1);
+  });
+
+  it('falls back to the terminal when the prior element is gone, but only with a live session', () => {
+    const { app, priorElement, terminalTextarea } = focusHarness();
+    app.openCommandPalette();
+    priorElement.isConnected = false;
+    app.closeCommandPalette();
+    expect(priorElement.focus).not.toHaveBeenCalled();
+    expect(terminalTextarea.focus).toHaveBeenCalledTimes(1);
+  });
+
+  it('never focuses the terminal from the welcome screen (a phone would pop the keyboard)', () => {
+    const { app, priorElement, terminalTextarea } = focusHarness();
+    app.activeSessionId = null;
+    app.openCommandPalette();
+    priorElement.isConnected = false;
+    app.closeCommandPalette();
+    expect(terminalTextarea.focus).not.toHaveBeenCalled();
+  });
+
+  it('does not restore focus to <body>, which is the bug itself', () => {
+    const { app, terminalTextarea, body, setActive } = focusHarness();
+    setActive(body);
+    app.openCommandPalette();
+    app.closeCommandPalette();
+    expect(terminalTextarea.focus).toHaveBeenCalledTimes(1);
+  });
+
+  it('restores focus on the session manager too, not just the palette', async () => {
+    const { app, elements, priorElement } = focusHarness();
+    elements.sessionManagerModal = { classList: { add: vi.fn(), remove: vi.fn() }, addEventListener: vi.fn() };
+    elements.sessionManagerSearch = { value: '', focus: vi.fn(), addEventListener: vi.fn() };
+    elements.sessionManagerList = { replaceChildren: vi.fn(), appendChild: vi.fn() };
+    app._loadSessionManagerList = vi.fn();
+    await app.openSessionManager();
+    app.closeSessionManager();
+    expect(priorElement.focus).toHaveBeenCalledTimes(1);
+  });
+});
+
 describe('panel close helpers', () => {
   it('closes panels when the mobile header helper is unavailable', () => {
     const CodemanApp = function CodemanApp(this: any) {};