refactor(display): extract shared rendering logic into renderer.py

- Add renderer.py with parse_ansi(), get_default_font_path(), render_to_pil()
- Update KittyDisplay and SixelDisplay to use shared renderer
- Enhance parse_ansi to handle full ANSI color codes (4-bit, 256-color)
- Update tests to use shared renderer functions

engine/display/backends/pygame.py

@@ -4,6 +4,8 @@ Pygame display backend - renders to a native application window.
 
 import time
 
+from engine.display.renderer import parse_ansi
+
 
 class PygameDisplay:
     """Pygame display backend - renders to native window.
@@ -141,10 +143,10 @@ class PygameDisplay:
             if row_idx >= self.height:
                 break
 
-            tokens = self._parse_ansi(line)
+            tokens = parse_ansi(line)
             x_pos = 0
 
-            for text, fg, bg in tokens:
+            for text, fg, bg, _bold in tokens:
                 if not text:
                     continue
 
@@ -168,72 +170,6 @@ class PygameDisplay:
             chars_in = sum(len(line) for line in buffer)
             monitor.record_effect("pygame_display", elapsed_ms, chars_in, chars_in)
 
-    def _parse_ansi(
-        self, text: str
-    ) -> list[tuple[str, tuple[int, int, int], tuple[int, int, int]]]:
-        """Parse ANSI text into tokens with fg/bg colors."""
-        tokens = []
-        current_text = ""
-        fg = (204, 204, 204)
-        bg = (0, 0, 0)
-        i = 0
-
-        ANSI_COLORS = {
-            0: (0, 0, 0),
-            1: (205, 49, 49),
-            2: (13, 188, 121),
-            3: (229, 229, 16),
-            4: (36, 114, 200),
-            5: (188, 63, 188),
-            6: (17, 168, 205),
-            7: (229, 229, 229),
-            8: (102, 102, 102),
-            9: (241, 76, 76),
-            10: (35, 209, 139),
-            11: (245, 245, 67),
-            12: (59, 142, 234),
-            13: (214, 112, 214),
-            14: (41, 184, 219),
-            15: (255, 255, 255),
-        }
-
-        while i < len(text):
-            char = text[i]
-
-            if char == "\x1b" and i + 1 < len(text) and text[i + 1] == "[":
-                if current_text:
-                    tokens.append((current_text, fg, bg))
-                    current_text = ""
-
-                i += 2
-                code = ""
-                while i < len(text):
-                    c = text[i]
-                    if c.isalpha():
-                        break
-                    code += c
-                    i += 1
-
-                if code:
-                    codes = code.split(";")
-                    for c in codes:
-                        if c == "0":
-                            fg = (204, 204, 204)
-                            bg = (0, 0, 0)
-                        elif c.isdigit():
-                            color_idx = int(c)
-                            if color_idx in ANSI_COLORS:
-                                fg = ANSI_COLORS[color_idx]
-                i += 1
-            else:
-                current_text += char
-                i += 1
-
-        if current_text:
-            tokens.append((current_text, fg, bg))
-
-        return tokens
-
     def clear(self) -> None:
         if self._screen and self._pygame:
             self._screen.fill((0, 0, 0))