Tab now moves the keyboard from the session list to the pane (was
Escape); Escape moves it back from the pane to the list, intercepted via
xterm's attachCustomKeyEventHandler so it never reaches the shell/app.
Matches the TUI's `tab`/`esc` pair; Ctrl+Q was ruled out since browsers
reserve it and never deliver it to page JS.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Ctrl+Shift+H moves the keyboard between the session list and the pane;
j/k walk the cards, Enter opens, Escape hands the pane back. The walk
skips expanded folder headers and stops on collapsed ones, matching the
TUI.