refactor: add DesignIR distillation pipeline

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

@@ -6,11 +6,10 @@ Capture these fields when known:
 
 - Natural-language request and normalized part family.
 - Units and dimensions.
-- Manufacturing intent: machining, printing, laser cutting, simulation, or concept.
-- Required primary and secondary output formats.
+- STEP is the fixed geometry artifact format.
 - New model versus modification, and existing source/artifact paths.
 - Part versus assembly, standard components, mating requirements, and motion relationships.
-- Required parameter controls, replay, semantic tags, or FreeCAD interchange.
+- Required parameter controls, replay, or semantic tags.
 - Geometry and visual validation targets.
 - Optional schema `2.0` generalized experience library. Never pass a case
   DesignIR, teacher STEP, source dimensions, coordinates, or surface references
@@ -23,13 +22,12 @@ Capture these fields when known:
 
 Record:
 
-- `selected_backend`: `build123d`, `simplecadapi`, or `cadam`.
+- `selected_backend`: `build123d` or `simplecadapi`.
 - Origin project and optional executable adapter.
 - `runner_skill`: installed Skill responsible for generation.
 - Ranked backend scores and human-readable reasons.
 - Fallback order.
 - Workflow profiles such as `requirement_refinement` and `visual_repair`.
-- Focused downstream Skills.
 - Any explicit override and its reason.
 - `operation`: create or modify; for modification also record the explicit
   source path and whether the route uses native parameter editing, local feature
@@ -47,7 +45,7 @@ Write `cad-task.json` beside the task artifacts with this minimum shape:
     "selected_backend": "build123d",
     "runner_skill": "cad",
     "project": "text-to-cad",
-    "fallback_order": ["simplecadapi", "cadam"],
+    "fallback_order": ["simplecadapi"],
     "workflow_profiles": ["requirement_refinement", "visual_repair"]
   },
   "source": {
@@ -56,12 +54,11 @@ Write `cad-task.json` beside the task artifacts with this minimum shape:
     "backend": "build123d"
   },
   "artifacts": [
-    {"path": "connecting_rod.step", "role": "primary"},
-    {"path": "connecting_rod.stl", "role": "secondary"}
+    {"path": "connecting_rod.step", "role": "primary"}
   ],
   "parameters": {},
   "experience": {
-    "library": "../../../cad-experience-library/library.json",
+    "library": "../../../designir-pipeline/workspace/promotion/promoted/library.json",
     "context_kind": "generalized_cad_experience_query",
     "methods_applied": []
   },
@@ -73,13 +70,14 @@ Write `cad-task.json` beside the task artifacts with this minimum shape:
 
 Paths are relative to the task directory unless an external input must remain absolute.
 Do not store authoritative model parameters in `cad-task.json`. Every part must
-have a sibling `model-spec.json` that owns its parameter values, reconstruction
-mode, parametric modification layer, and output paths. See `model-spec.md`.
+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 imported STEP, use `exact_step_base`: copy the explicitly supplied file
-into the task directory, record its checksum and geometry signature, and keep
-the imported B-Rep unchanged when the modification list is empty. This is an
-exact geometric base contract, not recovery of the original CAD feature tree.
+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.
 
 ## Backend adapter requirements