refactor: Engine updates and NX hooks improvements

optimization_engine:
- Updated nx_solver.py with improvements
- Enhanced solve_simulation.py
- Updated extractors/__init__.py
- Improved NX CAD hooks (expression_manager, feature_manager,
  geometry_query, model_introspection, part_manager)
- Enhanced NX CAE solver_manager hook

Documentation:
- Updated OP_01_CREATE_STUDY.md protocol
- Updated SYS_12_EXTRACTOR_LIBRARY.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

optimization_engine/solve_simulation.py

@@ -53,6 +53,111 @@ import NXOpen.Assemblies
 import NXOpen.CAE
 
 
+def extract_part_mass(theSession, part, output_dir):
+    """
+    Extract mass from a part using NX MeasureManager.
+
+    Writes mass to _temp_mass.txt and _temp_part_properties.json in output_dir.
+
+    Args:
+        theSession: NXOpen.Session
+        part: NXOpen.Part to extract mass from
+        output_dir: Directory to write temp files
+
+    Returns:
+        Mass in kg (float)
+    """
+    import json
+
+    results = {
+        'part_file': part.Name,
+        'mass_kg': 0.0,
+        'mass_g': 0.0,
+        'volume_mm3': 0.0,
+        'surface_area_mm2': 0.0,
+        'center_of_gravity_mm': [0.0, 0.0, 0.0],
+        'num_bodies': 0,
+        'success': False,
+        'error': None
+    }
+
+    try:
+        # Get all solid bodies
+        bodies = []
+        for body in part.Bodies:
+            if body.IsSolidBody:
+                bodies.append(body)
+
+        results['num_bodies'] = len(bodies)
+
+        if not bodies:
+            results['error'] = "No solid bodies found"
+            raise ValueError("No solid bodies found in part")
+
+        # Get the measure manager
+        measureManager = part.MeasureManager
+
+        # Get unit collection and build mass_units array
+        # API requires: [Area, Volume, Mass, Length] base units
+        uc = part.UnitCollection
+        mass_units = [
+            uc.GetBase("Area"),
+            uc.GetBase("Volume"),
+            uc.GetBase("Mass"),
+            uc.GetBase("Length")
+        ]
+
+        # Create mass properties measurement
+        measureBodies = measureManager.NewMassProperties(mass_units, 0.99, bodies)
+
+        if measureBodies:
+            results['mass_kg'] = measureBodies.Mass
+            results['mass_g'] = results['mass_kg'] * 1000.0
+
+            try:
+                results['volume_mm3'] = measureBodies.Volume
+            except:
+                pass
+
+            try:
+                results['surface_area_mm2'] = measureBodies.Area
+            except:
+                pass
+
+            try:
+                cog = measureBodies.Centroid
+                if cog:
+                    results['center_of_gravity_mm'] = [cog.X, cog.Y, cog.Z]
+            except:
+                pass
+
+            try:
+                measureBodies.Dispose()
+            except:
+                pass
+
+        results['success'] = True
+
+    except Exception as e:
+        results['error'] = str(e)
+        results['success'] = False
+
+    # Write results to JSON file
+    output_file = os.path.join(output_dir, "_temp_part_properties.json")
+    with open(output_file, 'w') as f:
+        json.dump(results, f, indent=2)
+
+    # Write simple mass value for backward compatibility
+    mass_file = os.path.join(output_dir, "_temp_mass.txt")
+    with open(mass_file, 'w') as f:
+        f.write(str(results['mass_kg']))
+
+    if not results['success']:
+        raise ValueError(results['error'])
+
+    return results['mass_kg']
+
+
 def find_or_open_part(theSession, part_path):
     """
     Find a part if already loaded, otherwise open it.
@@ -296,6 +401,15 @@ def solve_assembly_fem_workflow(theSession, sim_file_path, solution_name, expres
             partSaveStatus_blank.Dispose()
             print(f"[JOURNAL]   M1_Blank saved")
 
+            # STEP 2a: EXTRACT MASS FROM M1_BLANK
+            # Extract mass using MeasureManager after geometry is updated
+            print(f"[JOURNAL]   Extracting mass from M1_Blank...")
+            try:
+                mass_kg = extract_part_mass(theSession, workPart, working_dir)
+                print(f"[JOURNAL]   Mass extracted: {mass_kg:.6f} kg ({mass_kg * 1000:.2f} g)")
+            except Exception as mass_err:
+                print(f"[JOURNAL]   WARNING: Mass extraction failed: {mass_err}")
+
             updated_expressions = list(expression_updates.keys())
 
         except Exception as e: