feat: coarse_stride per sub-sampling top-level

Nuovo kernel JIT _jit_score_bitmap_rescored_strided: valuta solo
pixel su griglia stride x stride al top della piramide. NMS + fase
full-res recuperano precisione. Speed-up ~stride^2 sulla fase coarse,
specie su scene grandi (1920x1080).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pm2d/line_matcher.py

@@ -573,6 +573,7 @@ class LineShapeMatcher:
         verify_ncc: bool = True,
         verify_threshold: float = 0.4,
         coarse_angle_factor: int = 2,
+        coarse_stride: int = 1,
         scale_penalty: float = 0.0,
     ) -> list[Match]:
         """
@@ -645,13 +646,16 @@ class LineShapeMatcher:
                 end = min(n, i + half + 1)
                 neighbor_map[vi_c] = vi_sorted[start:end]
 
-        # Pruning varianti via top-level (parallelizzato) - solo coarse
+        # Pruning varianti via top-level (parallelizzato) - solo coarse.
+        # coarse_stride > 1: valuta solo 1 pixel ogni stride, ~stride² speed-up.
+        cs = max(1, int(coarse_stride))
+
         def _top_score(vi: int) -> tuple[int, float]:
             var = self.variants[vi]
             lvl = var.levels[min(top, len(var.levels) - 1)]
             score = _jit_score_bitmap_rescored(
                 spread_top, lvl.dx, lvl.dy, lvl.bin, bit_active_top,
-                bg_cache_top[var.scale],
+                bg_cache_top[var.scale], stride=cs,
             )
             return vi, float(score.max()) if score.size else -1.0