fix(canvas): Bug fixes for node movement, drag-drop, config panel, and introspection

- SpecRenderer: Add localNodes state with applyNodeChanges for smooth node dragging
- SpecRenderer: Fix getDefaultNodeData() - extractor uses 'custom_function' type with function definition
- SpecRenderer: Fix constraint default - use constraint_type instead of type
- CanvasView: Show config panel INSTEAD of chat when node selected (not blocked)
- NodeConfigPanelV2: Enable showHeader for code editor toolbar (Generate/Snippets/Validate/Test buttons)
- NodeConfigPanelV2: Pass studyId to IntrospectionPanel
- IntrospectionPanel: Accept studyId prop and use correct API endpoint
- optimization.py: Search multiple directories for model files including 1_setup/model/

atomizer-dashboard/frontend/src/components/canvas/SpecRenderer.tsx

@@ -10,7 +10,7 @@
  * P2.7-P2.10: SpecRenderer component with node/edge/selection handling
  */
 
-import { useCallback, useRef, useEffect, useMemo, DragEvent } from 'react';
+import { useCallback, useRef, useEffect, useMemo, useState, DragEvent } from 'react';
 import ReactFlow, {
   Background,
   Controls,
@@ -22,6 +22,7 @@ import ReactFlow, {
   NodeChange,
   EdgeChange,
   Connection,
+  applyNodeChanges,
 } from 'reactflow';
 import 'reactflow/dist/style.css';
 
@@ -74,8 +75,28 @@ function getDefaultNodeData(type: AddableNodeType, position: { x: number; y: num
     case 'extractor':
       return {
         name: `extractor_${timestamp}`,
-        type: 'custom',
+        type: 'custom_function',  // Must be valid ExtractorType
+        builtin: false,
         enabled: true,
+        // Custom function extractors need a function definition
+        function: {
+          name: 'extract',
+          source_code: `def extract(op2_path: str, config: dict = None) -> dict:
+    """
+    Custom extractor function.
+    
+    Args:
+        op2_path: Path to the OP2 results file
+        config: Optional configuration dict
+    
+    Returns:
+        Dictionary with extracted values
+    """
+    # TODO: Implement extraction logic
+    return {'value': 0.0}
+`,
+        },
+        outputs: [{ name: 'value', metric: 'custom' }],
         canvas_position: position,
       };
     case 'objective':
@@ -90,7 +111,8 @@ function getDefaultNodeData(type: AddableNodeType, position: { x: number; y: num
     case 'constraint':
       return {
         name: `constraint_${timestamp}`,
-        type: 'upper',
+        constraint_type: 'hard',  // Must be 'hard' or 'soft'
+        operator: '<=',
         limit: 1.0,
         source_extractor_id: null,
         source_output: null,
@@ -208,12 +230,23 @@ function SpecRendererInner({
     nodesRef.current = nodes;
   }, [nodes]);
 
+  // Track local node state for smooth dragging
+  const [localNodes, setLocalNodes] = useState(nodes);
+  
+  // Sync local nodes with spec-derived nodes when spec changes
+  useEffect(() => {
+    setLocalNodes(nodes);
+  }, [nodes]);
+
   // Handle node position changes
   const onNodesChange = useCallback(
     (changes: NodeChange[]) => {
       if (!editable) return;
 
-      // Handle position changes
+      // Apply changes to local state for smooth dragging
+      setLocalNodes((nds) => applyNodeChanges(changes, nds));
+
+      // Handle position changes - save to spec when drag ends
       for (const change of changes) {
         if (change.type === 'position' && change.position && change.dragging === false) {
           // Dragging ended - update spec
@@ -458,7 +491,7 @@ function SpecRendererInner({
       )}
 
       <ReactFlow
-        nodes={nodes}
+        nodes={localNodes}
         edges={edges}
         onNodesChange={onNodesChange}
         onEdgesChange={onEdgesChange}