fix(terminal): fix new tab auto-focus and NaN error on data before layout (#14357)

- Fix new tab not auto-focusing: add FocusNode to TerminalView and
  request focus when tab is selected via tab state listener
- Fix NaN error when data arrives before terminal view layout: buffer
  output data until terminal view has valid dimensions, flush on first
  valid resize callback

Signed-off-by: fufesou <linlong1266@gmail.com>

flutter/lib/desktop/pages/terminal_tab_page.dart

@@ -92,6 +92,7 @@ class _TerminalTabPageState extends State<TerminalTabPage> {
         key: ValueKey(tabKey),
         id: peerId,
         terminalId: terminalId,
+        tabKey: tabKey,
         password: password,
         isSharedPassword: isSharedPassword,
         tabController: tabController,