fix: address folder tree QA feedback — recursive filtering, folder creation, path display, remove flatten banner

1. Folder selection now recursively includes notes from subfolders
2. + button creates a new folder with inline rename (Tauri command + UI)
3. Note list items show full path when note is in a subdirectory
4. Remove flat vault migration banner and all related code (Rust commands,
   hook, component, smoke test) — subfolders are now first-class

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/FlatVaultMigrationBanner.tsx

@@ -1,37 +0,0 @@
-interface FlatVaultMigrationBannerProps {
-  strayFileCount: number
-  isMigrating: boolean
-  onMigrate: () => void
-  onDismiss: () => void
-}
-
-/**
- * Banner shown when the vault has files in non-protected subfolders.
- * Offers to flatten them to the vault root.
- */
-export function FlatVaultMigrationBanner({ strayFileCount, isMigrating, onMigrate, onDismiss }: FlatVaultMigrationBannerProps) {
-  return (
-    <div className="flex items-center gap-3 px-4 py-2 bg-amber-50 dark:bg-amber-950 border-b border-amber-200 dark:border-amber-800 text-sm" data-testid="migration-banner">
-      <span className="flex-1 text-amber-800 dark:text-amber-200">
-        {strayFileCount} note{strayFileCount !== 1 ? 's' : ''} found in subfolders.
-        Flatten to vault root for consistent scanning.
-      </span>
-      <button
-        className="px-3 py-1 text-xs font-medium rounded bg-amber-600 text-white hover:bg-amber-700 disabled:opacity-50"
-        onClick={onMigrate}
-        disabled={isMigrating}
-        data-testid="migration-flatten-btn"
-      >
-        {isMigrating ? 'Migrating...' : 'Flatten Now'}
-      </button>
-      <button
-        className="px-2 py-1 text-xs text-amber-600 dark:text-amber-400 hover:underline"
-        onClick={onDismiss}
-        disabled={isMigrating}
-        data-testid="migration-dismiss-btn"
-      >
-        Dismiss
-      </button>
-    </div>
-  )
-}

src/components/FolderTree.tsx

@@ -1,4 +1,4 @@
-import { useState, useCallback, memo } from 'react'
+import { useState, useCallback, useRef, useEffect, memo } from 'react'
 import { Folder, FolderOpen, CaretDown, CaretRight, Plus } from '@phosphor-icons/react'
 import type { FolderNode, SidebarSelection } from '../types'
 import { cn } from '@/lib/utils'
@@ -7,6 +7,7 @@ interface FolderTreeProps {
   folders: FolderNode[]
   selection: SidebarSelection
   onSelect: (selection: SidebarSelection) => void
+  onCreateFolder?: (name: string) => void
 }
 
 function FolderItem({
@@ -71,15 +72,31 @@ function FolderItem({
   )
 }
 
-export const FolderTree = memo(function FolderTree({ folders, selection, onSelect }: FolderTreeProps) {
+export const FolderTree = memo(function FolderTree({ folders, selection, onSelect, onCreateFolder }: FolderTreeProps) {
   const [sectionCollapsed, setSectionCollapsed] = useState(false)
   const [expanded, setExpanded] = useState<Record<string, boolean>>({})
+  const [isCreating, setIsCreating] = useState(false)
+  const [newFolderName, setNewFolderName] = useState('')
+  const inputRef = useRef<HTMLInputElement>(null)
 
   const toggleFolder = useCallback((path: string) => {
     setExpanded((prev) => ({ ...prev, [path]: !prev[path] }))
   }, [])
 
-  if (folders.length === 0) return null
+  useEffect(() => {
+    if (isCreating) inputRef.current?.focus()
+  }, [isCreating])
+
+  const handleCreateFolder = () => {
+    const name = newFolderName.trim()
+    if (name && onCreateFolder) {
+      onCreateFolder(name)
+    }
+    setIsCreating(false)
+    setNewFolderName('')
+  }
+
+  if (folders.length === 0 && !isCreating) return null
 
   return (
     <div style={{ padding: '8px 0' }}>
@@ -93,7 +110,14 @@ export const FolderTree = memo(function FolderTree({ folders, selection, onSelec
           {sectionCollapsed ? <CaretRight size={12} /> : <CaretDown size={12} />}
           <span className="text-[10px] font-semibold" style={{ letterSpacing: 0.5 }}>FOLDERS</span>
         </div>
-        <Plus size={12} className="text-muted-foreground" />
+        {onCreateFolder && (
+          <Plus
+            size={12}
+            className="text-muted-foreground hover:text-foreground"
+            onClick={(e) => { e.stopPropagation(); setIsCreating(true); setSectionCollapsed(false) }}
+            data-testid="create-folder-btn"
+          />
+        )}
       </button>
 
       {/* Tree */}
@@ -110,6 +134,24 @@ export const FolderTree = memo(function FolderTree({ folders, selection, onSelec
               onSelect={onSelect}
             />
           ))}
+          {isCreating && (
+            <div className="flex items-center gap-2" style={{ padding: '4px 8px' }}>
+              <Folder size={18} className="shrink-0 text-muted-foreground" />
+              <input
+                ref={inputRef}
+                className="flex-1 border border-border rounded bg-background px-1.5 py-0.5 text-[13px] text-foreground outline-none focus:border-primary"
+                value={newFolderName}
+                onChange={(e) => setNewFolderName(e.target.value)}
+                onKeyDown={(e) => {
+                  if (e.key === 'Enter') handleCreateFolder()
+                  if (e.key === 'Escape') { setIsCreating(false); setNewFolderName('') }
+                }}
+                onBlur={handleCreateFolder}
+                placeholder="Folder name"
+                data-testid="new-folder-input"
+              />
+            </div>
+          )}
         </div>
       )}
     </div>

src/components/NoteItem.tsx

@@ -129,6 +129,9 @@ export function NoteItem({ entry, isSelected, isMultiSelected = false, isHighlig
           {entry.title}
           <StateBadge archived={entry.archived} trashed={entry.trashed} />
         </div>
+        {entry.path.includes('/') && (
+          <div className="truncate text-[10px] text-muted-foreground" data-testid="note-path">{entry.path}</div>
+        )}
       </div>
       {entry.snippet && (
         <div className="mt-0.5 text-[12px] leading-[1.5] text-muted-foreground" data-testid="note-snippet" style={{ display: '-webkit-box', WebkitLineClamp: 2, WebkitBoxOrient: 'vertical', overflow: 'hidden' }}>

src/components/Sidebar.tsx

@@ -35,6 +35,7 @@ interface SidebarProps {
   onRenameSection?: (typeName: string, label: string) => void
   onToggleTypeVisibility?: (typeName: string) => void
   folders?: FolderNode[]
+  onCreateFolder?: (name: string) => void
   inboxCount?: number
   onCollapse?: () => void
 }
@@ -207,7 +208,7 @@ export const Sidebar = memo(function Sidebar({
   entries, selection, onSelect, onSelectNote, onCreateType, onCreateNewType,
   onCustomizeType, onUpdateTypeTemplate, onReorderSections, onRenameSection,
   onToggleTypeVisibility,
-  folders = [], inboxCount = 0, onCollapse,
+  folders = [], onCreateFolder, inboxCount = 0, onCollapse,
 }: SidebarProps) {
   const [collapsed, setCollapsed] = useState<Record<string, boolean>>({})
   const [customizeTarget, setCustomizeTarget] = useState<string | null>(null)
@@ -317,7 +318,7 @@ export const Sidebar = memo(function Sidebar({
         </DndContext>
 
         {/* Folder tree */}
-        <FolderTree folders={folders} selection={selection} onSelect={onSelect} />
+        <FolderTree folders={folders} selection={selection} onSelect={onSelect} onCreateFolder={onCreateFolder} />
       </nav>
 
       <ContextMenuOverlay pos={contextMenuPos} type={contextMenuType} innerRef={contextMenuRef} onOpenCustomize={(type) => { closeContextMenu(); setCustomizeTarget(type) }} onStartRename={handleStartRename} />