Drop named-position axis for grounded geometry (30B still mis-names positions)

Even the 30B mis-identifies named sex positions (doggy/cowgirl) from images, so
position_name is removed. The pose cluster is now purely observable geometry:
body_orientation enriched with facing direction (who faces whom), plus
limb_arrangement / contact_points / pose. The agent composes any named label from
these reliable primitives. 23 default axes. Docs/examples updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/AGENT_LOOP.md

@@ -61,7 +61,7 @@ Stdout (captured by the agent) is the report:
   "overall_score": 0.62,
   "mismatch_count": 1,
   "axes": {
-    "position_name":  {"verdict": "mismatch", "ref": "doggy style", "gen": "cowgirl"},
+    "body_orientation": {"verdict": "mismatch", "ref": "female on top, facing partner", "gen": "female on bottom"},
     "clothing_state": {"verdict": "partial",  "ref": "red lace lingerie", "gen": "plain bra"}
   },
   "prompt_used": "...",