fix(map): fail on blank rows inside a layer, keep trailing-space cells verbatim

tests/test_map.py

@@ -73,6 +73,35 @@ def test_rejects_ragged_rows(tmp_path: Path) -> None:
         load_map(_write(tmp_path, body))
 
 
+def test_rejects_blank_row_inside_layer(tmp_path: Path) -> None:
+    """A truly blank line inside a layer is a missing row -- an error, never
+    silently dropped (the old filter shrank the row count unnoticed)."""
+    body = _minimal_map().replace("  ###\n  #.#\n", "  ###\n\n  #.#\n")
+    with pytest.raises(MapValidationError, match="blank row"):
+        load_map(_write(tmp_path, body))
+
+
+def test_trailing_space_cells_are_kept(tmp_path: Path) -> None:
+    """With " " in the legend, trailing spaces are real cells: rstrip() must
+    not delete them (the layer keeps its full width)."""
+    body = (
+        '\nname: "Test"\nterrain: |\n  ...\n  .. \n'
+        'legend:\n'
+        '  ".": { type: floor, move_cost: 1 }\n'
+        '  " ": { type: floor, move_cost: 1 }\n'
+    )
+    spec = load_map(_write(tmp_path, body))
+    assert spec.terrain == ("...", ".. ")
+
+
+def test_rejects_trailing_space_without_legend_entry(tmp_path: Path) -> None:
+    """Without " " in the legend a padded row is ragged/unknown-char data,
+    reported as an error instead of silently stripped."""
+    body = _minimal_map().replace("  ###\n  #.#\n  ###\n", "  ### \n  #.# \n  ### \n")
+    with pytest.raises(MapValidationError):
+        load_map(_write(tmp_path, body))
+
+
 def test_rejects_non_five_foot_square_size(tmp_path: Path) -> None:
     """SRD Measuring Distance: one grid square is 5 ft; the engine geometry
     is hard-coded to that scale, so any other declared size is a load error