fix(canvas): Multiple fixes for drag-drop, undo/redo, and code generation

Drag-drop fixes:
- Fix Objective default data: use nested 'source' object with extractor_id/output_name
- Fix Constraint default data: use 'type' field (not constraint_type), 'threshold' (not limit)

Undo/Redo fixes:
- Remove dependency on isDirty flag (which is always false due to auto-save)
- Record snapshots based on actual spec changes via deep comparison

Code generation improvements:
- Update system prompt to support multiple extractor types:
  * OP2-based extractors for FEA results (stress, displacement, frequency)
  * Expression-based extractors for NX model values (dimensions, volumes)
  * Computed extractors for derived values (no FEA needed)
- Claude will now choose appropriate signature based on user's description

.claude/settings.local.json

@@ -62,7 +62,23 @@
       "Bash(xargs -I{} git ls-tree -r -l HEAD {})",
       "Bash(sort:*)",
       "Bash(C:Usersantoianaconda3envsatomizerpython.exe introspect_model.py)",
-      "Bash(xargs:*)"
+      "Bash(xargs:*)",
+      "Bash(ping:*)",
+      "Bash(C:Usersantoianaconda3envsatomizerpython.exe -c \"import requests; r = requests.post\\(''http://127.0.0.1:8001/api/claude/sessions'', json={''mode'': ''user''}\\); print\\(f''Status: {r.status_code}''\\); print\\(f''Response: {r.text}''\\)\")",
+      "Bash(start \"Atomizer Backend\" cmd /k C:UsersantoiAtomizerrestart_backend.bat)",
+      "Bash(start \"Test Backend\" cmd /c \"cd /d C:\\\\Users\\\\antoi\\\\Atomizer\\\\atomizer-dashboard\\\\backend && C:\\\\Users\\\\antoi\\\\anaconda3\\\\Scripts\\\\activate.bat atomizer && python -m uvicorn api.main:app --port 8002\")",
+      "Bash(C:Usersantoianaconda3envsatomizerpython.exe C:UsersantoiAtomizertest_backend.py)",
+      "Bash(start \"Backend 8002\" C:UsersantoiAtomizerstart_backend_8002.bat)",
+      "Bash(C:Usersantoianaconda3envsatomizerpython.exe -c \"from api.main import app; print\\(''Import OK''\\)\")",
+      "Bash(find:*)",
+      "Bash(npx tailwindcss:*)",
+      "Bash(C:Usersantoianaconda3envsatomizerpython.exe -c \"from pathlib import Path; p = Path\\(''C:/Users/antoi/Atomizer/studies''\\) / ''M1_Mirror/m1_mirror_cost_reduction_lateral''; print\\(''exists:'', p.exists\\(\\), ''path:'', p\\)\")",
+      "Bash(C:Usersantoianaconda3envsatomizerpython.exe -c \"import sys, json; d=json.load\\(sys.stdin\\); print\\(''Study:'', d.get\\(''meta'',{}\\).get\\(''study_name'',''N/A''\\)\\); print\\(''Design Variables:''\\); [print\\(f''  - {dv[\"\"name\"\"]} \\({dv[\"\"expression_name\"\"]}\\)''\\) for dv in d.get\\(''design_variables'',[]\\)]\")",
+      "Bash(C:Usersantoianaconda3envsatomizerpython.exe -m py_compile:*)",
+      "Skill(ralph-loop:ralph-loop)",
+      "Skill(ralph-loop:ralph-loop:*)",
+      "mcp__Claude_in_Chrome__computer",
+      "mcp__Claude_in_Chrome__navigate"
     ],
     "deny": [],
     "ask": []