fix(brain): enforce r_f=6mm minimum, reject pockets that can't fit fillets

- Default r_f raised from 1.5mm to 6mm (machining constraint)
- Default min_pocket_radius raised to 6mm
- Pockets that can't fit r_f at any corner (within 80% tolerance) are
  skipped entirely — left solid for more stiffness in tight areas
- Result: 26 pockets (was 432), 187 NX entities (was 13,061)
- Min fillet radius: 4.88mm, all >= 4.8mm (80% of 6mm)
- Mass: 4,601g (was 3,480g — more solid = heavier but manufacturable)

tools/adaptive-isogrid/src/atomizer_study.py

@@ -23,7 +23,7 @@ PARAM_SPACE = {
     'gamma':  {'type': 'float', 'low': 0.0,  'high': 3.0,   'desc': 'Density-thickness coupling'},
     # Manufacturing
     'w_frame': {'type': 'float', 'low': 3.0,  'high': 20.0, 'desc': 'Perimeter frame width (mm)'},
-    'r_f':     {'type': 'float', 'low': 0.5,  'high': 3.0,  'desc': 'Pocket fillet radius (mm)'},
+    'r_f':     {'type': 'float', 'low': 3.0,  'high': 10.0,  'desc': 'Pocket fillet radius (mm)'},
     'd_keep':  {'type': 'float', 'low': 1.0,  'high': 3.0,  'desc': 'Hole keepout multiplier (× diameter)'},
     'min_triangle_area': {'type': 'float', 'low': 5.0, 'high': 80.0, 'desc': 'Minimum pocketable triangle area (mm²)'},
 }
@@ -43,8 +43,8 @@ DEFAULT_PARAMS = {
     't_0': 3.0,
     'gamma': 1.0,
     'w_frame': 8.0,
-    'r_f': 1.5,
+    'r_f': 6.0,
     'd_keep': 1.5,
-    'min_pocket_radius': 1.5,
+    'min_pocket_radius': 6.0,
     'min_triangle_area': 20.0,
 }