feat: flexible intake — deferred variables + prepared sessions (#103)

* feat: flexible intake — deferred variables + prepared sessions

Remove blocking intake form modal. Variables are now filled inline during
flow execution or pre-filled via prepared sessions. Adds PATCH /sessions/{id}/variables
endpoint, POST /sessions/prepare for session pre-staging, inline variable prompts
in StepDetail, editable Session Variables panel, and "Prepared for You" dashboard section.

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

* fix: pass treeData directly to startSession to avoid stale state

setTree(treeData) hasn't committed when startSession runs immediately
after, so tree is still null and getStepsFromTree returns []. This
caused the step detail area to render empty on new session start.

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

* feat: wire PrepareSessionModal entry point in Flow Library

Add "Prepare session" button (clipboard icon) to grid, list, and table
views for procedural/maintenance flows. Clicking fetches tree intake
fields and account members, then opens PrepareSessionModal.

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/TreeLibraryPage.tsx

@@ -7,11 +7,13 @@ import { treesApi } from '@/api/trees'
 import { categoriesApi } from '@/api/categories'
 import { foldersApi } from '@/api/folders'
 import { sessionsApi } from '@/api/sessions'
-import type { TreeListItem, CategoryListItem, FolderListItem, Session } from '@/types'
+import type { TreeListItem, CategoryListItem, FolderListItem, Session, IntakeFormField } from '@/types'
 import { FolderEditModal } from '@/components/library/FolderEditModal'
 import { ForkModal } from '@/components/library/ForkModal'
 import { ExportFlowModal } from '@/components/library/ExportFlowModal'
 import { ImportFlowModal } from '@/components/library/ImportFlowModal'
+import { PrepareSessionModal } from '@/components/procedural/PrepareSessionModal'
+import { accountsApi } from '@/api/accounts'
 import { ConfirmDialog } from '@/components/common/ConfirmDialog'
 import { TreeGridView } from '@/components/library/TreeGridView'
 import { TreeListView } from '@/components/library/TreeListView'
@@ -83,6 +85,13 @@ export function TreeLibraryPage() {
   const [showImportModal, setShowImportModal] = useState(false)
   const [exportTarget, setExportTarget] = useState<TreeListItem | null>(null)
 
+  // Prepare session modal state
+  const [prepareTarget, setPrepareTarget] = useState<{
+    tree: TreeListItem
+    intakeFields: IntakeFormField[]
+    teamMembers: { id: string; name: string; email: string }[]
+  } | null>(null)
+
   // AI builder state
 
   const { aiEnabled } = useCachedQuota()
@@ -268,6 +277,24 @@ export function TreeLibraryPage() {
     if (tree) setExportTarget(tree)
   }
 
+  const handlePrepareSession = async (tree: TreeListItem) => {
+    try {
+      const [treeDetail, members] = await Promise.all([
+        treesApi.get(tree.id),
+        accountsApi.getMembers().catch(() => []),
+      ])
+      setPrepareTarget({
+        tree,
+        intakeFields: treeDetail.intake_form || [],
+        teamMembers: members
+          .filter(m => m.is_active)
+          .map(m => ({ id: m.id, name: m.name, email: m.email })),
+      })
+    } catch {
+      toast.error('Failed to load flow details')
+    }
+  }
+
   const hasActiveFilters =
     selectedCategoryId || selectedTags.length > 0 || searchQuery || selectedFolderId
 
@@ -436,7 +463,7 @@ export function TreeLibraryPage() {
                     </p>
                     <p className="text-sm text-muted-foreground">
                       {s.client_name && `${s.client_name} · `}
-                      Started {formatTimeAgo(s.started_at)}
+                      {s.started_at ? `Started ${formatTimeAgo(s.started_at)}` : 'Not started'}
                     </p>
                   </div>
                   <div className="flex items-center gap-2">
@@ -498,6 +525,7 @@ export function TreeLibraryPage() {
                 <TreeGridView
                   trees={trees}
                   onStartSession={handleStartSession}
+                  onPrepareSession={handlePrepareSession}
                   onTagClick={handleTagClick}
                   onFolderCreated={handleCreateFolder}
                   onDeleteTree={(tree) => {
@@ -515,6 +543,7 @@ export function TreeLibraryPage() {
                 <TreeListView
                   trees={trees}
                   onStartSession={handleStartSession}
+                  onPrepareSession={handlePrepareSession}
                   onTagClick={handleTagClick}
                   onFolderCreated={handleCreateFolder}
                   onDeleteTree={(tree) => {
@@ -532,6 +561,7 @@ export function TreeLibraryPage() {
                 <TreeTableView
                   trees={trees}
                   onStartSession={handleStartSession}
+                  onPrepareSession={handlePrepareSession}
                   onTagClick={handleTagClick}
                   onFolderCreated={handleCreateFolder}
                   onDeleteTree={(tree) => {
@@ -604,6 +634,18 @@ export function TreeLibraryPage() {
           onClose={() => { setShowImportModal(false); loadTrees() }}
         />
       )}
+
+      {prepareTarget && (
+        <PrepareSessionModal
+          isOpen
+          onClose={() => setPrepareTarget(null)}
+          treeId={prepareTarget.tree.id}
+          treeName={prepareTarget.tree.name}
+          intakeFields={prepareTarget.intakeFields}
+          teamMembers={prepareTarget.teamMembers}
+          onPrepared={() => setPrepareTarget(null)}
+        />
+      )}
     </div>
     </div>
   )