tell tmux to refresh-client on resize

tmux doesn't re-read the PTY winsize on SIGWINCH. After the ioctl
resize, call tmux refresh-client -C cols,rows to update tmux's
internal window dimensions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.pql/pql-plan.json

@@ -1,5 +1,5 @@
 {
-  "exported_at": "2026-05-01T11:03:51Z",
+  "exported_at": "2026-05-01T11:11:26Z",
   "decisions": [
     {
       "id": "D-1",

lib/builtin/claude/src/claude_pane.dart

@@ -242,8 +242,10 @@ class _ClaudePaneState extends State<ClaudePane> {
     _resizeTimer = Timer(const Duration(milliseconds: 150), () {
       final id = _paneId;
       if (id == null) return;
-      print('[resize] cols=$cols rows=$rows');
       _ipc()?.request('pane.resize', args: {'id': id, 'cols': cols, 'rows': rows});
+      // tmux doesn't re-read PTY winsize on SIGWINCH — it needs an
+      // explicit refresh-client to update its internal window size.
+      Process.run('tmux', ['refresh-client', '-C', '$cols,$rows']);
     });
   }