fix: complete session persistence overhaul (Codex 5.2)

1. Implemented auto-selection of tasks in MultiXV2 to prevent empty initial state.
2. Added force-loading logic for task session messages with debouncing.
3. Updated session-actions to return full assistant text and immediately persist native messages.
4. Fixed caching logic in instance-shell2 to retain active task sessions in memory.

packages/ui/src/components/instance/instance-shell2.tsx

@@ -683,7 +683,25 @@ Now analyze the project and report your findings.`
   })
 
   const handleSessionSelect = (sessionId: string) => {
-    setActiveSession(props.instance.id, sessionId)
+    if (sessionId === "info") {
+      setActiveSession(props.instance.id, sessionId)
+      return
+    }
+
+    const instanceSessions = sessions().get(props.instance.id)
+    const session = instanceSessions?.get(sessionId)
+
+    if (session?.parentId) {
+      setActiveParentSession(props.instance.id, session.parentId)
+      const parentSession = instanceSessions?.get(session.parentId)
+      const matchingTask = parentSession?.tasks?.find((task) => task.taskSessionId === sessionId)
+      if (matchingTask) {
+        setActiveTask(props.instance.id, session.parentId, matchingTask.id)
+      }
+      return
+    }
+
+    setActiveParentSession(props.instance.id, sessionId)
   }
 
 
@@ -731,6 +749,7 @@ Now analyze the project and report your findings.`
     const sessionsMap = activeSessions()
     const parentId = parentSessionIdForInstance()
     const activeId = activeSessionIdForInstance()
+    const instanceSessions = sessions().get(props.instance.id)
     setCachedSessionIds((current) => {
       const next: string[] = []
       const append = (id: string | null) => {
@@ -743,6 +762,16 @@ Now analyze the project and report your findings.`
       append(parentId)
       append(activeId)
 
+      const parentSessionId = parentId || activeId
+      const parentSession = parentSessionId ? instanceSessions?.get(parentSessionId) : undefined
+      const activeTaskId = parentSession?.activeTaskId
+      if (activeTaskId && parentSession?.tasks?.length) {
+        const activeTask = parentSession.tasks.find((task) => task.id === activeTaskId)
+        if (activeTask?.taskSessionId) {
+          append(activeTask.taskSessionId)
+        }
+      }
+
       const limit = parentId ? SESSION_CACHE_LIMIT + 1 : SESSION_CACHE_LIMIT
       const trimmed = next.length > limit ? next.slice(0, limit) : next
       const trimmedSet = new Set(trimmed)