feat: add adaptive isogrid tool — project foundations

- Python Brain: density field, constrained Delaunay triangulation,
  pocket profiles, profile assembly, validation modules
- NX Hands: skeleton scripts for geometry extraction, AFEM setup,
  per-iteration solve (require NX environment to develop)
- Atomizer integration: 15-param space definition, objective function
- Technical spec, README, sample test geometry, requirements.txt
- Architecture: Python Brain + NX Hands + Atomizer Manager

tools/adaptive-isogrid/src/nx/build_interface_model.py

@@ -0,0 +1,28 @@
+"""
+NXOpen script — Build Interface Model (Model A) for Assembly FEM.
+
+ONE-TIME: Creates spider elements (RBE2/RBE3) at each hole + edge BC nodes.
+Exports interface_nodes.json for the iteration script.
+
+NOTE: Skeleton — requires NX environment for development.
+See docs/technical-spec.md Section 4.2 for full pseudocode.
+"""
+
+
+def build_interface_model(geometry_json_path, fem_part):
+    """
+    Build Model A: spider elements at each hole + edge BC nodes.
+    
+    For each hole:
+    - Center node (master)
+    - N circumference nodes (~1 per 2mm of circumference)
+    - RBE2 (rigid) or RBE3 (distributing) spider
+    
+    For plate boundary:
+    - Edge nodes at ~3mm spacing
+    
+    Exports interface_nodes.json with all node IDs and coordinates.
+    """
+    raise NotImplementedError(
+        "Develop inside NX Simcenter. See docs/technical-spec.md Section 4.2."
+    )