fix: align CM93 coverage and hazard runtime with OpenCPN

tools/cm95_s52_presentation_conservation_audit.py

@@ -383,22 +383,14 @@ def _load_coverage_unions(
                 _to_mercator_geom(geom)
             )
 
-        pieces = []
-        for cell in cells:
-            cid = int(cell["id"])
-            if by_cell.get(cid):
-                pieces.append(unary_union(by_cell[cid]))
-                continue
-            minx, miny = lonlat_to_mercator(
-                float(cell["bbox_min_lon"]),
-                float(cell["bbox_min_lat"]),
-            )
-            maxx, maxy = lonlat_to_mercator(
-                float(cell["bbox_max_lon"]),
-                float(cell["bbox_max_lat"]),
-            )
-            pieces.append(box(minx, miny, maxx, maxy))
-
+        # Keep the independent audit scope identical to OpenCPN/Builder
+        # coverage semantics: only explicit M_COVR rows define valid coverage.
+        # Never substitute the chart_cell index bbox for a missing M_COVR.
+        pieces = [
+            unary_union(by_cell[cid])
+            for cid in sorted(by_cell)
+            if by_cell[cid]
+        ]
         if pieces:
             result[scale] = unary_union(pieces).intersection(
                 broad_box_m