fix(shortcuts): stop Ctrl+PageUp/Down from leaking to xterm

preventDefault on the window-capture listener does not block xterm's
own keydown listener, which translates Ctrl+PageUp/PageDown into
\e[5~ / \e[6~ and writes them to the shell (and trips the terminal
activity indicator). Stop propagation so the event never reaches the
focused terminal.

Co-authored-by: Orca <help@stably.ai>

src/renderer/src/components/Terminal.tsx

@@ -771,7 +771,16 @@ function Terminal(): React.JSX.Element | null {
         !e.repeat
       ) {
         if (handleSwitchTerminalTab(e.code === 'PageDown' ? 1 : -1)) {
+          // Why: stop propagation in addition to preventDefault. Unlike
+          // Cmd+Shift+]/[ (xterm ignores Meta-modified keys by default),
+          // xterm actively translates plain Ctrl+PageUp/PageDown into the
+          // \e[5~ / \e[6~ escape sequences and writes them to the shell.
+          // preventDefault on the window-capture listener does not stop
+          // xterm's own keydown listener on its textarea, so we must stop
+          // the event before it reaches the focused terminal.
           e.preventDefault()
+          e.stopPropagation()
+          e.stopImmediatePropagation()
         }
       }
     }