refactor: simplify distillation data layout

text-to-cad/skills/cad-router/references/backend-contract.md

@@ -58,7 +58,7 @@ Write `cad-task.json` beside the task artifacts with this minimum shape:
   ],
   "parameters": {},
   "experience": {
-    "library": "../../../designir-pipeline/workspace/promotion/promoted/library.json",
+    "library": "../../../designir-pipeline/output/library.json",
     "context_kind": "generalized_cad_experience_query",
     "methods_applied": []
   },
@@ -74,10 +74,10 @@ have a sibling `*.designir.json` that owns its coordinate system, datums,
 parameters, expressions, features, constraints, edit interface, and validation
 contract. See `designir-2.0.md`.
 
-For an uploaded STEP, keep teacher geometry in the protected ingestion and
-acceptance workspace. The reconstruction task contains private evidence,
-DesignIR, backend source, and rebuilt STEP but no teacher STEP or imported
-B-Rep.
+For an uploaded STEP, keep teacher geometry in `designir-pipeline/input/` and
+all private evidence, DesignIR candidates, rebuilds, and acceptance reports in
+`designir-pipeline/runs/`. The reconstruction task receives evidence but no
+teacher STEP or imported B-Rep.
 
 ## Backend adapter requirements