feat(canvas): Studio Enhancement Phase 3 & 4 - undo/redo and Monaco editor

Phase 3 - Undo/Redo System:
- Create generic useUndoRedo hook with configurable options
- Add localStorage persistence for per-study history (max 30 steps)
- Create useSpecUndoRedo hook integrating with useSpecStore
- Add useUndoRedoKeyboard hook for Ctrl+Z/Ctrl+Y shortcuts
- Add undo/redo buttons to canvas header with tooltips
- Debounced history recording (1s delay after changes)

Phase 4 - Monaco Code Editor:
- Create CodeEditorPanel component with Monaco editor
- Add Python syntax highlighting and auto-completion
- Include pyNastran/OP2 specific completions
- Add Claude AI code generation integration (placeholder)
- Include code validation/run functionality
- Show output variables preview section
- Add copy-to-clipboard and generation prompt UI

Dependencies:
- Add @monaco-editor/react package

Technical:
- All TypeScript checks pass
- All 15 unit tests pass
- Production build successful

atomizer-dashboard/frontend/src/pages/CanvasView.tsx

@@ -1,6 +1,6 @@
 import { useState, useEffect, useCallback } from 'react';
 import { useNavigate, useParams, useSearchParams } from 'react-router-dom';
-import { ClipboardList, Download, Trash2, Layers, Home, ChevronRight, Save, RefreshCw, Zap, MessageSquare, X, Folder, SlidersHorizontal } from 'lucide-react';
+import { ClipboardList, Download, Trash2, Layers, Home, ChevronRight, Save, RefreshCw, Zap, MessageSquare, X, Folder, SlidersHorizontal, Undo2, Redo2 } from 'lucide-react';
 import { AtomizerCanvas } from '../components/canvas/AtomizerCanvas';
 import { SpecRenderer } from '../components/canvas/SpecRenderer';
 import { NodePalette } from '../components/canvas/palette/NodePalette';
@@ -12,6 +12,7 @@ import { NodeConfigPanelV2 } from '../components/canvas/panels/NodeConfigPanelV2
 import { ChatPanel } from '../components/canvas/panels/ChatPanel';
 import { useCanvasStore } from '../hooks/useCanvasStore';
 import { useSpecStore, useSpec, useSpecLoading, useSpecIsDirty, useSelectedNodeId } from '../hooks/useSpecStore';
+import { useSpecUndoRedo, useUndoRedoKeyboard } from '../hooks/useSpecUndoRedo';
 import { useStudy } from '../context/StudyContext';
 import { useChat } from '../hooks/useChat';
 import { CanvasTemplate } from '../lib/canvas/templates';
@@ -54,6 +55,13 @@ export function CanvasView() {
   const { setSelectedStudy, studies } = useStudy();
   const { clearSpec, setSpecFromWebSocket } = useSpecStore();
 
+  // Undo/Redo for spec mode
+  const undoRedo = useSpecUndoRedo();
+  const { undo, redo, canUndo, canRedo, historyLength } = undoRedo;
+
+  // Enable keyboard shortcuts for undo/redo (Ctrl+Z, Ctrl+Y)
+  useUndoRedoKeyboard(undoRedo);
+
   // Active study ID comes ONLY from URL - don't auto-load from context
   // This ensures /canvas shows empty canvas, /canvas/{id} shows the study
   const activeStudyId = urlStudyId;
@@ -318,6 +326,39 @@ export function CanvasView() {
             </button>
           )}
 
+          {/* Undo/Redo Buttons (spec mode only) */}
+          {useSpecMode && activeStudyId && (
+            <>
+              <div className="w-px h-6 bg-dark-600" />
+              <div className="flex items-center gap-1">
+                <button
+                  onClick={undo}
+                  disabled={!canUndo}
+                  className={`p-1.5 rounded-lg transition-colors ${
+                    canUndo
+                      ? 'text-dark-200 hover:bg-dark-700 hover:text-white'
+                      : 'text-dark-600 cursor-not-allowed'
+                  }`}
+                  title={`Undo (Ctrl+Z)${historyLength > 0 ? ` - ${historyLength} steps` : ''}`}
+                >
+                  <Undo2 size={16} />
+                </button>
+                <button
+                  onClick={redo}
+                  disabled={!canRedo}
+                  className={`p-1.5 rounded-lg transition-colors ${
+                    canRedo
+                      ? 'text-dark-200 hover:bg-dark-700 hover:text-white'
+                      : 'text-dark-600 cursor-not-allowed'
+                  }`}
+                  title="Redo (Ctrl+Y)"
+                >
+                  <Redo2 size={16} />
+                </button>
+              </div>
+            </>
+          )}
+
           <button
             onClick={() => setShowTemplates(true)}
             className="px-3 py-1.5 bg-primary-600 hover:bg-primary-500 text-white text-sm rounded-lg transition-colors flex items-center gap-1.5"