feat: helper set_angle_range_around + angle_tolerance hint in auto_tune

LineShapeMatcher.set_angle_range_around(center, tol): restringe
angle_range a (center-tol, center+tol). Use case: feeder/posizionamento
meccanico noto a priori. Esempio:
    m.set_angle_range_around(0, 20)  # cerca solo in [-20, +20]

auto_tune accetta angle_tolerance_deg + angle_center_deg: emette
angle_min/angle_max ristretti se hint fornito. Cache key include
hint per non collidere con tune default.

Beneficio misurato: angle_step=5 deg, template 80x80
- range 360°: 72 varianti
- range ±15°: 6 varianti (12x meno = matching ~12x piu veloce)

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

pm2d/line_matcher.py

@@ -192,6 +192,26 @@ class LineShapeMatcher:
                 np.array(picked_y, np.int32),
                 np.array(picked_b, np.int8))
 
+    def set_angle_range_around(
+        self, center_deg: float, tolerance_deg: float,
+    ) -> None:
+        """Restringe angle_range a (center - tol, center + tol).
+
+        Comodo helper per scenari in cui l'orientamento del pezzo e'
+        noto a priori entro ±tolerance_deg (es. feeder vibrante con
+        guida meccanica). Riduce drasticamente le varianti generate
+        in train(): es. ±15° vs 360° = 24x meno varianti, training
+        e matching molto piu veloci.
+
+        Esempio:
+            m.set_angle_range_around(0, 20)   # cerca solo in [-20, +20]
+            m.train(template)
+        """
+        self.angle_range_deg = (
+            float(center_deg - tolerance_deg),
+            float(center_deg + tolerance_deg),
+        )
+
     def _scale_list(self) -> list[float]:
         s0, s1 = self.scale_range
         if s0 >= s1 or self.scale_step <= 0: