wip: preserve local engine and agent workflow changes before ganjihong refactor integration

backend/app/cad_agent/application/authoring_guidance.py

@@ -0,0 +1,16 @@
+"""Prompt material for the model-facing Authoring CDSL contract."""
+from __future__ import annotations
+
+from functools import lru_cache
+from pathlib import Path
+
+
+_GUIDANCE = Path(__file__).resolve().parents[4] / "agent" / "skills" / "cad-authoring" / "SKILL.md"
+
+
+@lru_cache(maxsize=1)
+def load_authoring_guidance() -> str:
+    try:
+        return _GUIDANCE.read_text(encoding="utf-8")[:12_000]
+    except OSError:
+        return "Use cad.author.v1 only. Never create runtime IDs or selector tokens."