feat: Phase 3 — Library page create dropdown + AI Builder + pin wiring

- Replace single Create link with dropdown menu (3 flow types + AI Builder)
- Wire pinnedFlowsStore to all view components
- AI Builder modal integration via useCachedQuota hook

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

frontend/src/pages/TreeLibraryPage.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState, useCallback } from 'react'
 import { useNavigate, Link, useSearchParams } from 'react-router-dom'
-import { Plus, X, RotateCcw, Play } from 'lucide-react'
+import { Plus, X, RotateCcw, Play, ChevronDown, Sparkles, FolderTree, ListOrdered, Wrench } from 'lucide-react'
 import { treesApi } from '@/api/trees'
 import { categoriesApi } from '@/api/categories'
 import { foldersApi } from '@/api/folders'
@@ -17,6 +17,9 @@ import { cn, safeGetItem } from '@/lib/utils'
 import { getSessionResumePath } from '@/lib/routing'
 import { usePermissions } from '@/hooks/usePermissions'
 import { useUserPreferencesStore } from '@/store/userPreferencesStore'
+import { usePinnedFlowsStore, selectPinnedTreeIds, selectPinLoadingTreeIds } from '@/store/pinnedFlowsStore'
+import { useCachedQuota } from '@/hooks/useCachedQuota'
+import { AIFlowBuilderModal } from '@/components/ai-builder/AIFlowBuilderModal'
 import { toast } from '@/lib/toast'
 
 export function TreeLibraryPage() {
@@ -69,6 +72,17 @@ export function TreeLibraryPage() {
   // Fork state
   const [isForkingTree, setIsForkingTree] = useState(false)
 
+  // Create menu & AI builder state
+  const [showCreateMenu, setShowCreateMenu] = useState(false)
+  const [showAIBuilder, setShowAIBuilder] = useState(false)
+  const { aiEnabled } = useCachedQuota()
+
+  // Pin store
+  const pinnedTreeIds = usePinnedFlowsStore(selectPinnedTreeIds)
+  const pinLoadingTreeIds = usePinnedFlowsStore(selectPinLoadingTreeIds)
+  const togglePin = usePinnedFlowsStore((s) => s.toggle)
+  const loadPinned = usePinnedFlowsStore((s) => s.load)
+
   // Repeat Last Session
   const lastSessionData = (() => {
     const raw = safeGetItem('last-session')
@@ -102,6 +116,9 @@ export function TreeLibraryPage() {
       .catch((err) => console.error('Failed to load incomplete sessions:', err))
   }, [])
 
+  // Load pinned flows
+  useEffect(() => { loadPinned() }, [loadPinned])
+
   const dismissSession = (sessionId: string) => {
     const next = new Set(dismissedSessionIds)
     next.add(sessionId)
@@ -263,16 +280,78 @@ export function TreeLibraryPage() {
               </p>
             </div>
             {canCreateTrees && (
-              <Link
-                to={typeFilter === 'procedural' ? '/flows/new' : typeFilter === 'maintenance' ? '/flows/new?type=maintenance' : '/trees/new'}
-                className={cn(
-                  'flex items-center gap-2 rounded-md bg-gradient-brand px-4 py-2 text-sm font-medium text-white shadow-lg shadow-primary/20',
-                  'hover:opacity-90'
+              <div className="relative">
+                <button
+                  onClick={() => setShowCreateMenu(!showCreateMenu)}
+                  className={cn(
+                    'flex items-center gap-2 rounded-md bg-gradient-brand px-4 py-2 text-sm font-medium text-white shadow-lg shadow-primary/20',
+                    'hover:opacity-90'
+                  )}
+                >
+                  <Plus className="h-4 w-4" />
+                  Create New
+                  <ChevronDown className="h-3.5 w-3.5" />
+                </button>
+                {showCreateMenu && (
+                  <>
+                    <div className="fixed inset-0 z-10" onClick={() => setShowCreateMenu(false)} />
+                    <div className="absolute right-0 z-20 mt-1 w-56 rounded-lg border border-border bg-card p-1 shadow-xl backdrop-blur-sm">
+                      <Link
+                        to="/trees/new"
+                        onClick={() => setShowCreateMenu(false)}
+                        className="flex items-center gap-3 rounded-md px-3 py-2.5 text-sm text-foreground hover:bg-accent"
+                      >
+                        <FolderTree className="h-4 w-4 text-muted-foreground" />
+                        <div>
+                          <div className="font-medium">Troubleshooting Tree</div>
+                          <div className="text-xs text-muted-foreground">Branching decision flow</div>
+                        </div>
+                      </Link>
+                      <Link
+                        to="/flows/new"
+                        onClick={() => setShowCreateMenu(false)}
+                        className="flex items-center gap-3 rounded-md px-3 py-2.5 text-sm text-foreground hover:bg-accent"
+                      >
+                        <ListOrdered className="h-4 w-4 text-muted-foreground" />
+                        <div>
+                          <div className="font-medium">Procedural Flow</div>
+                          <div className="text-xs text-muted-foreground">Step-by-step procedure</div>
+                        </div>
+                      </Link>
+                      <Link
+                        to="/flows/new?type=maintenance"
+                        onClick={() => setShowCreateMenu(false)}
+                        className="flex items-center gap-3 rounded-md px-3 py-2.5 text-sm text-foreground hover:bg-accent"
+                      >
+                        <Wrench className="h-4 w-4 text-amber-400" />
+                        <div>
+                          <div className="font-medium">Maintenance Flow</div>
+                          <div className="text-xs text-muted-foreground">Scheduled multi-target tasks</div>
+                        </div>
+                      </Link>
+                      {aiEnabled && (
+                        <>
+                          <div className="my-1 border-t border-border" />
+                          <button
+                            type="button"
+                            onClick={() => {
+                              setShowCreateMenu(false)
+                              setShowAIBuilder(true)
+                            }}
+                            className="flex w-full items-center gap-3 rounded-md px-3 py-2.5 text-sm text-foreground hover:bg-accent"
+                          >
+                            <Sparkles className="h-4 w-4 text-primary" />
+                            <div className="text-left">
+                              <div className="font-medium">Build with AI</div>
+                              <div className="text-xs text-muted-foreground">AI-assisted flow creation</div>
+                            </div>
+                          </button>
+                        </>
+                      )}
+                    </div>
+                  </>
                 )}
-              >
-                <Plus className="h-4 w-4" />
-                {typeFilter === 'procedural' ? 'New Project' : typeFilter === 'maintenance' ? 'New Maintenance Flow' : 'Create Flow'}
-              </Link>
+              </div>
             )}
           </div>
 
@@ -474,6 +553,9 @@ export function TreeLibraryPage() {
                     setShowDeleteConfirm(true)
                   }}
                   onForkTree={handleForkTree}
+                  pinnedTreeIds={pinnedTreeIds}
+                  onTogglePin={togglePin}
+                  pinLoadingTreeIds={pinLoadingTreeIds}
                 />
               )}
               {treeLibraryView === 'list' && (
@@ -487,6 +569,9 @@ export function TreeLibraryPage() {
                     setShowDeleteConfirm(true)
                   }}
                   onForkTree={handleForkTree}
+                  pinnedTreeIds={pinnedTreeIds}
+                  onTogglePin={togglePin}
+                  pinLoadingTreeIds={pinLoadingTreeIds}
                 />
               )}
               {treeLibraryView === 'table' && (
@@ -505,6 +590,9 @@ export function TreeLibraryPage() {
                     )
                   }}
                   onForkTree={handleForkTree}
+                  pinnedTreeIds={pinnedTreeIds}
+                  onTogglePin={togglePin}
+                  pinLoadingTreeIds={pinLoadingTreeIds}
                 />
               )}
             </>
@@ -538,6 +626,14 @@ export function TreeLibraryPage() {
         confirmVariant="destructive"
         isLoading={isDeleting}
       />
+
+      {/* AI Builder Modal */}
+      {showAIBuilder && (
+        <AIFlowBuilderModal
+          isOpen={showAIBuilder}
+          onClose={() => setShowAIBuilder(false)}
+        />
+      )}
     </div>
   )
 }