TextFrame(fix[display]): Use shutil for terminal size detection

why: curses KEY_RESIZE only fires on getch(), missing resize events
     when terminal is resized but no key is pressed
what:
- Replace stdscr.getmaxyx() with shutil.get_terminal_size()
- Remove KEY_RESIZE handling (now redundant)
- Update test to verify shutil.get_terminal_size() is called

This follows Rich's approach: query terminal size directly via
ioctl(TIOCGWINSZ) on each loop iteration, which works reliably
in tmux and other terminal multiplexers.

Author: tony

src/libtmux/textframe/core.py

@@ -8,6 +8,7 @@
 
 import contextlib
 import curses
+import shutil
 import sys
 import typing as t
 from dataclasses import dataclass, field
@@ -250,7 +251,10 @@ def _curses_display(self, stdscr: curses.window) -> None:
 
         while True:
             stdscr.clear()
-            max_y, max_x = stdscr.getmaxyx()
+
+            # Query terminal size directly (handles resize without signals)
+            term_size = shutil.get_terminal_size()
+            max_x, max_y = term_size.columns, term_size.lines
 
             # Calculate scroll bounds
             max_scroll_y = max(0, len(lines) - max_y + 1)

tests/textframe/test_display.py

@@ -137,3 +137,27 @@ def test_status_line_displayed(self, mock_curses: None) -> None:
             if len(call[0]) >= 3 and "q:quit" in str(call[0][2])
         ]
         assert len(status_calls) > 0, "Status line should be displayed"
+
+    def test_terminal_resize_via_shutil(self, mock_curses: None) -> None:
+        """Verify terminal size is queried via shutil.get_terminal_size().
+
+        This approach works reliably in tmux/multiplexers because it directly
+        queries the terminal via ioctl(TIOCGWINSZ) on each loop iteration,
+        rather than relying on curses KEY_RESIZE events.
+        """
+        import os
+
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        mock_stdscr = MagicMock()
+        mock_stdscr.getch.return_value = ord("q")
+
+        # Mock shutil.get_terminal_size to return specific dimensions
+        with patch(
+            "libtmux.textframe.core.shutil.get_terminal_size",
+            return_value=os.terminal_size((120, 40)),
+        ) as mock_get_size:
+            frame._curses_display(mock_stdscr)
+            # Verify shutil.get_terminal_size was called
+            mock_get_size.assert_called()