Booleans: a prism cut beside the target's other faces takes the exact 2D route in a column (#1629)

Thanks @phanoob.

tests/robustness/goldens.json

@@ -66,7 +66,7 @@
   "62": {"area":8771.003732,"bodies":1,"edges":60,"error":null,"faces":23,"outcome":"ok","rejected":0,"shells":1,"steps":["extruded profile","cut cylinder","circular pattern","cut box","cut box","join cylinder"],"unsupported":2,"volume":40107.001728},
   "63": {"area":3198.797259,"bodies":1,"edges":84,"error":null,"faces":30,"outcome":"ok","rejected":1,"shells":1,"steps":["revolved section","join box","cut cylinder","hole","cut cylinder","join box","fillet"],"unsupported":0,"volume":7075.892751},
   "64": {"area":4088.335645,"bodies":1,"edges":36,"error":null,"faces":14,"outcome":"ok","rejected":0,"shells":1,"steps":["extruded profile","fillet","join cylinder"],"unsupported":0,"volume":8495.220295},
-  "65": {"area":8442.175249,"bodies":1,"edges":33,"error":null,"faces":13,"outcome":"ok","rejected":0,"shells":1,"steps":["box","cut cylinder","fillet","rectangular pattern","circular pattern","circular pattern","fillet","cut box"],"unsupported":0,"volume":45117.305023},
+  "65": {"area":8436.255548,"bodies":1,"edges":37,"error":null,"faces":15,"outcome":"ok","rejected":0,"shells":1,"steps":["box","cut cylinder","fillet","rectangular pattern","circular pattern","circular pattern","fillet","cut box"],"unsupported":0,"volume":45143.475817},
   "66": {"area":9222.76638,"bodies":1,"edges":99,"error":null,"faces":37,"outcome":"ok","rejected":0,"shells":1,"steps":["extruded profile","join box","join box","join box","cut sphere","cut box"],"unsupported":1,"volume":35217.203139},
   "67": {"area":7943.46222,"bodies":2,"edges":88,"error":null,"faces":37,"outcome":"ok","rejected":0,"shells":2,"steps":["extruded profile","cut cylinder","hole","join cylinder","join box","hole","chamfer","rectangular pattern"],"unsupported":2,"volume":27607.962186},
   "68": {"area":7338.675126,"bodies":1,"edges":36,"error":null,"faces":14,"outcome":"ok","rejected":2,"shells":1,"steps":["extruded profile","hole","hole","rectangular pattern","rectangular pattern","fillet","circular pattern"],"unsupported":0,"volume":29780.741772},
@@ -124,6 +124,7 @@
   {"reason":"#1390: a chamfer of a convex edge that would grow the part is refused (TooLarge). Seed 57's 0.5 mm chamfer on the sphere cut's rim, which grew the part since #391 reordered its steps, is now refused, so the run goes on to its later steps and ends ok (16017.21 mm³, 24 faces)","seeds":[57]},
   {"reason":"Seed 83 builds: a shell splits a saddle corner (convex and concave edges in turn) into two corners","seeds":[83]},
   {"reason":"seed 15 now cuts around a sealed void","seeds":[15]},
-  {"reason":"#1490: when the last-resort nudge fails both ways, two more screw axes are tried; seed 63's final box join (its face 0.00005 mm off the half-ring's cut face) now builds instead of being refused with an implausible volume, and the design goes on to its fillet","seeds":[63]}
+  {"reason":"#1490: when the last-resort nudge fails both ways, two more screw axes are tried; seed 63's final box join (its face 0.00005 mm off the half-ring's cut face) now builds instead of being refused with an implausible volume, and the design goes on to its fillet","seeds":[63]},
+  {"reason":"a prism cut in a column round the tool (prism_local): seed 65's rectangular pattern (step 4, a second half-cylinder groove overlapping the first, in a block with a rounded vertical edge) is now built by the exact 2D route in a column clear of the round, where the B-rep tries left it with split edges. The step's part has the 10 faces, 24 edges and 16 vertices it should (28 edges and 18 vertices before), and its volume is 45145.383 mm³ against 45145.214 (exactly 45145.103, both within the mesh measure); the generator then picks other edges for its step 7 fillet, so the run ends on another design (45143.48 mm³, 15 faces)","seeds":[65]}
  ]
 }