feat(coords): Chunk-Namen als Planquadrat A1 bis L12

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

tools/extract/leonida/coords.py

@@ -2,6 +2,8 @@
 
 Spiegelt src/world/coords.js. Beide Seiten müssen dieselben Werte liefern.
 """
+import re
+
 TILE_PX = 256
 WORLD_HALF = 16384
 CHUNK_SIZE = 250
@@ -26,3 +28,23 @@ def mosaic_origin_px() -> tuple[int, int]:
 
 def pixel_to_world(px: int, py: int) -> tuple[float, float]:
     return (SLICE["x0"] + px, SLICE["y1"] - py)
+
+
+CHUNKS_PER_SIDE = (SLICE["x1"] - SLICE["x0"]) // CHUNK_SIZE   # 12
+CHUNK_COLUMNS = "ABCDEFGHIJKL"
+_CHUNK_NAME = re.compile(r"^([A-La-l])([1-9]\d?)$")
+
+
+def chunk_name(i: int, j: int) -> str | None:
+    """Planquadrat-Name wie src/world/coords.js: Spalte A–L aus i, Zeile 1–12 aus j. A1 = Nordwest."""
+    if not (0 <= i < CHUNKS_PER_SIDE and 0 <= j < CHUNKS_PER_SIDE):
+        return None
+    return f"{CHUNK_COLUMNS[i]}{j + 1}"
+
+
+def parse_chunk_name(name: str) -> tuple[int, int] | None:
+    """Umkehrung von chunk_name. Akzeptiert Kleinschreibung, None außerhalb A1–L12."""
+    match = _CHUNK_NAME.match(str(name))
+    if not match or int(match.group(2)) > CHUNKS_PER_SIDE:
+        return None
+    return CHUNK_COLUMNS.index(match.group(1).upper()), int(match.group(2)) - 1