feat: Add E11 Part Mass extractor, document pyNastran mass accuracy issue

New E11 Part Mass Extractor:
- Add nx_journals/extract_part_mass_material.py - NX journal using
  NXOpen.MeasureManager.NewMassProperties() for accurate geometry-based mass
- Add optimization_engine/extractors/extract_part_mass_material.py - Python
  wrapper that reads JSON output from journal
- Add E11 entry to extractors/catalog.json

Documentation Updates:
- SYS_12_EXTRACTOR_LIBRARY.md: Add mass accuracy warning noting pyNastran
  get_mass_breakdown() under-reports ~7% on hex-dominant meshes with
  tet/pyramid fill elements. E11 (geometry .prt) should be preferred over
  E4 (BDF) unless material is overridden at FEM level.
- 01_CHEATSHEET.md: Add mass extraction tip

V14 Config:
- Expand design variable bounds (blank_backface_angle max 4.5°,
  whiffle_triangle_closeness max 80mm, whiffle_min max 60mm)

Testing showed:
- E11 from .prt: 97.66 kg (accurate - matches NX GUI)
- E4 pyNastran get_mass_breakdown(): 90.73 kg (~7% under-reported)

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

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

optimization_engine/extractors/catalog.json

@@ -34,5 +34,19 @@
       "metric": "total"
     },
     "signature": "2f58f241a96afb1f"
+  },
+  "e11_part_mass_material": {
+    "name": "extract_part_mass_material",
+    "filename": "extract_part_mass_material.py",
+    "action": "extract_part_mass_material",
+    "domain": "cad_extraction",
+    "description": "Extract mass, volume, surface area, CoG, and material from NX .prt files via NXOpen.MeasureManager",
+    "params": {
+      "result_type": "part_mass",
+      "metric": "total",
+      "requires_journal": "nx_journals/extract_part_mass_material.py"
+    },
+    "signature": "e11_part_mass_material",
+    "notes": "Requires running NX journal first: run_journal.exe nx_journals/extract_part_mass_material.py <prt_file> -args <prt_path> <output_dir>"
   }
 }