feat(display): add Kitty graphics backend and improve font detection

- Add KittyDisplay using kitty's native graphics protocol
- Improve cross-platform font detection for SixelDisplay
- Add run-kitty mise task for testing kitty backend
- Add kitty_test.py for testing graphics protocol

kitty_test.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+"""Test script for Kitty graphics display."""
+
+import sys
+
+
+def test_kitty_simple():
+    """Test simple Kitty graphics output with embedded PNG."""
+    import base64
+
+    # Minimal 1x1 red pixel PNG (pre-encoded)
+    # This is a tiny valid PNG with a red pixel
+    png_red_1x1 = (
+        b"\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x00"
+        b"\x01\x00\x00\x00\x01\x08\x02\x00\x00\x00\x90wS\xde"
+        b"\x00\x00\x00\x0cIDATx\x9cc\xf8\xcf\xc0\x00\x00\x00"
+        b"\x03\x00\x01\x00\x05\xfe\xd4\x00\x00\x00\x00IEND\xaeB`\x82"
+    )
+
+    encoded = base64.b64encode(png_red_1x1).decode("ascii")
+
+    graphic = f"\x1b_Gf=100,t=d,s=1,v=1,c=1,r=1;{encoded}\x1b\\"
+    sys.stdout.buffer.write(graphic.encode("utf-8"))
+    sys.stdout.flush()
+
+    print("\n[If you see a red dot above, Kitty graphics is working!]")
+    print("[If you see nothing or garbage, it's not working]")
+
+
+if __name__ == "__main__":
+    test_kitty_simple()