oracle: rebless two fixtures moved by roundoff of the new elimination order (#212)

buckle-plate-square/lambda moves 3.0e-9 relative and plastic-hinge-cantilever/collapse_force
2.7e-8 relative: the graph dissection now orders these meshes, so the factor sums in another
order. Both stay at the same error against their references.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

tests/oracle/buckle-plate-square/fixture.json

@@ -3,7 +3,7 @@
   "values": {
     "lambda": {
       "band": 3.6152397073587395e-10,
-      "value": 0.3601281681211783
+      "value": 0.36012816702934053
     }
   }
 }

tests/oracle/plastic-hinge-cantilever/fixture.json

@@ -2,8 +2,8 @@
   "note": "FieldCraft's accepted results for this case, written by `cargo xtask oracle --bless`. A result outside its band fails CI.",
   "values": {
     "collapse_force": {
-      "band": 3.2260685847425373e-7,
-      "value": -322.6068584742537
+      "band": 3.226068671283815e-7,
+      "value": -322.6068671283815
     }
   }
 }