fix: resolve tree_structure type compatibility for shared session views

- Use TreeStructure & Record<string, unknown> intersection for JSONB flexibility
- Add explicit cast in SharedSessionTreePreview for recursive node rendering

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

frontend/src/components/session/SharedSessionTreePreview.tsx

@@ -80,7 +80,7 @@ export function SharedSessionTreePreview({
         <h3 className="text-sm font-semibold text-white">Tree Structure</h3>
       </div>
       <div className="max-h-[600px] overflow-y-auto py-2">
-        <TreeNode node={treeStructure} depth={0} pathTaken={pathTaken} />
+        <TreeNode node={treeStructure as unknown as Record<string, unknown>} depth={0} pathTaken={pathTaken} />
       </div>
     </div>
   )

frontend/src/pages/SharedSessionPage.tsx

@@ -232,7 +232,7 @@ export function SharedSessionPage() {
           <div className="lg:col-span-2">
             <SessionTimeline
               decisions={data.decisions}
-              treeType={data.tree_structure?.tree_type}
+              treeType={data.tree_structure?.tree_type as string | undefined}
               startedAt={data.started_at}
               completedAt={data.completed_at}
               showCopyButtons={false}

frontend/src/types/session.ts

@@ -156,7 +156,7 @@ export interface SharedSessionView {
   session_id: string
   tree_name: string
   tree_description: string | null
-  tree_structure: TreeStructure
+  tree_structure: TreeStructure & Record<string, unknown>
   path_taken: string[]
   decisions: DecisionRecord[]
   custom_steps: CustomStep[]