refactor: Update forms for inline safety, add MetadataSidePanel, update layout

- NodeFormDecision: option reorder via onUpdate (no premature store writes)
- NodePicker: add allowCreate prop (default true) to hide Create New options
  during inline canvas editing, preventing side-effect node creation
- MetadataSidePanel: 320px right slide-in overlay wrapping TreeMetadataForm,
  closes on backdrop click, close button, and Escape key
- TreeEditorLayout: Flow mode now renders full-width TreeCanvas + MetadataSidePanel
  overlay; Code mode unchanged (Monaco + preview split)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/tree-editor/MetadataSidePanel.tsx

@@ -0,0 +1,66 @@
+import { useEffect } from 'react'
+import { X } from 'lucide-react'
+import { TreeMetadataForm } from './TreeMetadataForm'
+
+interface MetadataSidePanelProps {
+  isOpen: boolean
+  onClose: () => void
+}
+
+export function MetadataSidePanel({ isOpen, onClose }: MetadataSidePanelProps) {
+  // Close on Escape key
+  useEffect(() => {
+    if (!isOpen) return
+
+    const handleKeyDown = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') {
+        onClose()
+      }
+    }
+
+    document.addEventListener('keydown', handleKeyDown)
+    return () => document.removeEventListener('keydown', handleKeyDown)
+  }, [isOpen, onClose])
+
+  if (!isOpen) return null
+
+  return (
+    <>
+      {/* Backdrop — click to close */}
+      <div
+        className="fixed inset-0 z-40 bg-background/40 backdrop-blur-sm"
+        onClick={onClose}
+        aria-hidden="true"
+      />
+
+      {/* Side panel — slides in from right */}
+      <div
+        className="fixed right-0 top-0 z-50 flex h-full w-80 flex-col border-l border-border bg-card shadow-xl"
+        role="dialog"
+        aria-label="Flow metadata"
+      >
+        {/* Panel header */}
+        <div className="flex items-center justify-between border-b border-border px-4 py-3">
+          <h2 className="text-sm font-semibold text-foreground font-heading">
+            Flow Details
+          </h2>
+          <button
+            type="button"
+            onClick={onClose}
+            className="rounded p-1.5 text-muted-foreground hover:bg-accent hover:text-foreground"
+            aria-label="Close metadata panel"
+          >
+            <X className="h-4 w-4" />
+          </button>
+        </div>
+
+        {/* Scrollable metadata form */}
+        <div className="flex-1 overflow-y-auto px-4 py-4">
+          <TreeMetadataForm />
+        </div>
+      </div>
+    </>
+  )
+}
+
+export default MetadataSidePanel

frontend/src/components/tree-editor/NodeFormDecision.tsx

@@ -16,7 +16,7 @@ const indexToLetter = (index: number): string => {
 }
 
 export function NodeFormDecision({ node, onUpdate }: NodeFormDecisionProps) {
-  const { reorderOptions, validationErrors } = useTreeEditorStore()
+  const { validationErrors } = useTreeEditorStore()
   const isRootNode = node.id === 'root'
 
   const questionError = validationErrors.find(
@@ -51,7 +51,12 @@ export function NodeFormDecision({ node, onUpdate }: NodeFormDecisionProps) {
   }
 
   const handleReorderOptions = (fromIndex: number, toIndex: number) => {
-    reorderOptions(node.id, fromIndex, toIndex)
+    // Mutate local draft via onUpdate (backward-compatible: modal path relays to store,
+    // canvas path updates local draft without writing to store early)
+    const newOptions = [...(node.options || [])]
+    const [moved] = newOptions.splice(fromIndex, 1)
+    newOptions.splice(toIndex, 0, moved)
+    onUpdate({ options: newOptions })
   }
 
   return (

frontend/src/components/tree-editor/NodePicker.tsx

@@ -35,6 +35,9 @@ interface NodePickerProps {
   error?: string
   /** Callback when a new node is created (receives the new node ID) */
   onNodeCreated?: (nodeId: string) => void
+  /** Whether to show the "Create New Node" options. Default: true.
+   *  Set to false in inline canvas editing to prevent premature store writes. */
+  allowCreate?: boolean
 }
 
 export function NodePicker({
@@ -46,7 +49,8 @@ export function NodePicker({
   className,
   label,
   error,
-  onNodeCreated
+  onNodeCreated,
+  allowCreate = true
 }: NodePickerProps) {
   const { getAvailableTargetNodes, addNode, updateNode } = useTreeEditorStore()
   const availableNodes = getAvailableTargetNodes(excludeNodeId)
@@ -201,12 +205,14 @@ export function NodePicker({
           >
             <option value="">{placeholder}</option>
 
-            {/* Create new options */}
-            <optgroup label="Create New Node">
-              <option value={CREATE_DECISION}>+ New Decision (question)</option>
-              <option value={CREATE_ACTION}>+ New Action (task)</option>
-              <option value={CREATE_SOLUTION}>+ New Solution (endpoint)</option>
-            </optgroup>
+            {/* Create new options — hidden when allowCreate=false (e.g. canvas inline editing) */}
+            {allowCreate && (
+              <optgroup label="Create New Node">
+                <option value={CREATE_DECISION}>+ New Decision (question)</option>
+                <option value={CREATE_ACTION}>+ New Action (task)</option>
+                <option value={CREATE_SOLUTION}>+ New Solution (endpoint)</option>
+              </optgroup>
+            )}
 
             {/* Existing nodes grouped by type */}
             {groupedNodes.decisions.length > 0 && (

frontend/src/components/tree-editor/TreeEditorLayout.tsx

@@ -1,7 +1,7 @@
 import { lazy, Suspense } from 'react'
-import { TreeMetadataForm } from './TreeMetadataForm'
-import { NodeList } from './NodeList'
 import { TreePreviewPanel } from '@/components/tree-preview/TreePreviewPanel'
+import { TreeCanvas } from './TreeCanvas'
+import { MetadataSidePanel } from './MetadataSidePanel'
 import { useTreeEditorStore } from '@/store/treeEditorStore'
 import { cn } from '@/lib/utils'
 
@@ -12,9 +12,15 @@ const CodeModeEditor = lazy(() =>
 
 interface TreeEditorLayoutProps {
   isMobile?: boolean
+  isMetadataOpen?: boolean
+  onCloseMetadata?: () => void
 }
 
-export function TreeEditorLayout({ isMobile = false }: TreeEditorLayoutProps) {
+export function TreeEditorLayout({
+  isMobile = false,
+  isMetadataOpen = false,
+  onCloseMetadata = () => {},
+}: TreeEditorLayoutProps) {
   const editorMode = useTreeEditorStore(s => s.editorMode)
 
   return (
@@ -26,7 +32,7 @@ export function TreeEditorLayout({ isMobile = false }: TreeEditorLayoutProps) {
     >
       {editorMode === 'code' ? (
         <>
-          {/* Code Mode: Monaco editor (60%) + Preview (40%) */}
+          {/* Code Mode: Monaco editor (60%) + Preview (40%) — unchanged */}
           <div className={cn(
             'flex flex-col overflow-hidden border-border',
             isMobile ? 'h-full w-full border-b' : 'w-3/5 border-r'
@@ -50,24 +56,16 @@ export function TreeEditorLayout({ isMobile = false }: TreeEditorLayoutProps) {
         </>
       ) : (
         <>
-          {/* Flow Mode: Form editor (60%) + Preview (40%) */}
-          <div className={cn(
-            'flex flex-col overflow-y-auto border-border',
-            isMobile ? 'h-full w-full border-b' : 'w-3/5 border-r'
-          )}>
-            <div className="space-y-4 p-4">
-              <TreeMetadataForm />
-              <NodeList />
-            </div>
+          {/* Flow Mode: Full-width visual canvas */}
+          <div className="flex-1 overflow-hidden">
+            <TreeCanvas />
           </div>
 
-          {/* Right Panel - Preview */}
-          <div className={cn(
-            'flex-1 overflow-hidden bg-accent/50',
-            isMobile ? 'hidden' : 'block'
-          )}>
-            <TreePreviewPanel />
-          </div>
+          {/* Metadata side panel — overlays the canvas from the right */}
+          <MetadataSidePanel
+            isOpen={isMetadataOpen}
+            onClose={onCloseMetadata}
+          />
         </>
       )}
     </div>