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)

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)