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/kitty.py

@@ -1,98 +1,10 @@
 """
-Kitty graphics display backend - renders using kitty's graphics protocol.
+Kitty graphics display backend - renders using kitty's native graphics protocol.
 """
 
 import time
 
-
-def _parse_ansi(
-    text: str,
-) -> list[tuple[str, tuple[int, int, int], tuple[int, int, int], bool]]:
-    """Parse ANSI text into tokens with fg/bg colors.
-
-    Returns list of (text, fg_rgb, bg_rgb, bold).
-    """
-    tokens = []
-    current_text = ""
-    fg = (204, 204, 204)
-    bg = (0, 0, 0)
-    bold = False
-    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, bold))
-                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)
-                        bold = False
-                    elif c == "1":
-                        bold = True
-                    elif c.isdigit():
-                        color_idx = int(c)
-                        if color_idx in ANSI_COLORS:
-                            fg = ANSI_COLORS[color_idx]
-                    elif c.startswith("38;5;"):
-                        idx = int(c.split(";")[-1])
-                        if idx < 256:
-                            fg = (
-                                (idx >> 5) * 51,
-                                ((idx >> 2) & 7) * 51,
-                                (idx & 3) * 85,
-                            )
-                    elif c.startswith("48;5;"):
-                        idx = int(c.split(";")[-1])
-                        if idx < 256:
-                            bg = (
-                                (idx >> 5) * 51,
-                                ((idx >> 2) & 7) * 51,
-                                (idx & 3) * 85,
-                            )
-            i += 1
-        else:
-            current_text += char
-            i += 1
-
-    if current_text:
-        tokens.append((current_text, fg, bg, bold))
-
-    return tokens
+from engine.display.renderer import get_default_font_path, parse_ansi
 
 
 def _encode_kitty_graphic(image_data: bytes, width: int, height: int) -> bytes:
@@ -141,8 +53,6 @@ class KittyDisplay:
     def _get_font_path(self) -> str | None:
         """Get font path from env or detect common locations."""
         import os
-        import sys
-        from pathlib import Path
 
         if self._font_path:
             return self._font_path
@@ -152,49 +62,11 @@ class KittyDisplay:
             self._font_path = env_font
             return env_font
 
-        def search_dir(base_path: str) -> str | None:
-            if not os.path.exists(base_path):
-                return None
-            if os.path.isfile(base_path):
-                return base_path
-            for font_file in Path(base_path).rglob("*"):
-                if font_file.suffix.lower() in (".ttf", ".otf", ".ttc"):
-                    name = font_file.stem.lower()
-                    if "geist" in name and ("nerd" in name or "mono" in name):
-                        return str(font_file)
-            return None
+        font_path = get_default_font_path()
+        if font_path:
+            self._font_path = font_path
 
-        search_dirs = []
-
-        if sys.platform == "darwin":
-            search_dirs.extend(
-                [os.path.expanduser("~/Library/Fonts/"), "/System/Library/Fonts/"]
-            )
-        elif sys.platform == "win32":
-            search_dirs.extend(
-                [
-                    os.path.expanduser(
-                        "~\\AppData\\Local\\Microsoft\\Windows\\Fonts\\"
-                    ),
-                    "C:\\Windows\\Fonts\\",
-                ]
-            )
-        else:
-            search_dirs.extend(
-                [
-                    os.path.expanduser("~/.local/share/fonts/"),
-                    os.path.expanduser("~/.fonts/"),
-                    "/usr/share/fonts/",
-                ]
-            )
-
-        for search_dir_path in search_dirs:
-            found = search_dir(search_dir_path)
-            if found:
-                self._font_path = found
-                return found
-
-        return None
+        return self._font_path
 
     def show(self, buffer: list[str]) -> None:
         import sys
@@ -230,7 +102,7 @@ class KittyDisplay:
             if row_idx >= self.height:
                 break
 
-            tokens = _parse_ansi(line)
+            tokens = parse_ansi(line)
             x_pos = 0
             y_pos = row_idx * self.cell_height