fix(coords): Chunk-Namen korrekt für Float-Indizes und Newlines

- chunk_name: Reject float/bool indices like JavaScript (Number.isInteger)
- parse_chunk_name: Use fullmatch instead of match($) to reject strings with trailing newlines
- Add invalidIndices fixture cases to catch these edge cases in both languages

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

tools/extract/tests/test_coords.py

@@ -43,3 +43,8 @@ def test_chunk_names_round_trip_for_all_144_chunks():
     for i in range(12):
         for j in range(12):
             assert parse_chunk_name(chunk_name(i, j)) == (i, j)
+
+
+def test_chunk_names_reject_invalid_index_types():
+    for i, j in NAMES["invalidIndices"]:
+        assert chunk_name(i, j) is None