oracle: 2D cases (Kirsch plane stress, Lamé plane strain and axisymmetric, rotating disc and cylinder, NAFEMS LE1 with quad8) and J2 uniaxial explicit

The pending 2D LE1 case becomes a real one; the plasticity cases stay
pending with what they still need (static J2 for the collapse pressure,
the transcribed measurements for the Taylor bar).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

tests/oracle/taylor-bar/expected.json

@@ -3,7 +3,7 @@
  "kind": "experiment",
  "source": "Wilkins and Guinan, 'Impact of cylinders on a rigid boundary', Journal of Applied Physics 44 (1973) 1200–1206 (final length and mushroom diameter vs impact speed)",
  "status": "pending",
- "requires": "large-deformation plasticity and contact (M10 X2/X3)",
+ "requires": "the measured final shapes, to be transcribed from the paper (explicit Johnson–Cook plasticity is in)",
  "quantities": [
   {
    "id": "final_length",