feat(ai): persist agent sessions and request context

prisma/schema.prisma

@@ -28,6 +28,7 @@ model User {
   studentChatThreads ChatThread[] @relation("ChatThreadStudent")
   assignedChatThreads ChatThread[] @relation("ChatThreadInstructor")
   chatMessages ChatMessage[]
+  agentSessions AgentSession[]
   platformControlSessions PlatformControlSession[]
   platformControlQueueEntries PlatformControlQueueEntry[]
   studioRepositories StudioRepository[]
@@ -177,6 +178,7 @@ model Course {
   studentProgress  CourseStudentProgress[]
   studentWeekProgress CourseStudentWeekProgress[]
   chatThreads      ChatThread[]
+  agentSessions    AgentSession[]
   enrollments       StudentEnrollment[]
   instructorCurriculumSettings InstructorCurriculumSetting[]
   instructorCurriculumWeekOverrides InstructorCurriculumWeekOverride[]
@@ -579,6 +581,7 @@ model CourseWeek {
   references  CourseWeekReference[]
   modules     CourseWeekModule[]
   chatThreads ChatThread[]
+  agentSessions AgentSession[]
   submissionScores SubmissionScore[]
   submissionTotalScores SubmissionTotalScore[]
 
@@ -835,3 +838,75 @@ model AiChatRun {
   @@index([status, createdAt])
   @@map("ai_chat_runs")
 }
+
+model AgentSession {
+  id             String         @id @default(uuid()) @db.Uuid
+  courseId       String         @map("course_id") @db.Uuid
+  weekId         String?        @map("week_id") @db.Uuid
+  studentId      String         @map("student_id") @db.Uuid
+  status         String         @default("ACTIVE")
+  title          String?
+  createdAt      DateTime       @default(now()) @map("created_at") @db.Timestamptz(3)
+  updatedAt      DateTime       @updatedAt @map("updated_at") @db.Timestamptz(3)
+  lastActivityAt DateTime       @default(now()) @map("last_activity_at") @db.Timestamptz(3)
+  course         Course         @relation(fields: [courseId], references: [id], onDelete: Cascade)
+  week           CourseWeek?    @relation(fields: [weekId], references: [id], onDelete: SetNull)
+  student        User           @relation(fields: [studentId], references: [id], onDelete: Cascade)
+  messages       AgentMessage[]
+
+  @@index([studentId, courseId, weekId, status, lastActivityAt])
+  @@index([courseId, lastActivityAt])
+  @@map("agent_sessions")
+}
+
+model AgentMessage {
+  id              String        @id @default(uuid()) @db.Uuid
+  sessionId       String        @map("session_id") @db.Uuid
+  clientMessageId String        @map("client_message_id")
+  role            String
+  content         String
+  provider        String?
+  model           String?
+  summary         String?
+  explanation     String?
+  actionPlan      Json?         @map("action_plan")
+  createModule    Json?         @map("create_module")
+  applyState      String?       @map("apply_state")
+  applyError      String?       @map("apply_error")
+  usage           Json?
+  createdAt       DateTime      @default(now()) @map("created_at") @db.Timestamptz(3)
+  updatedAt       DateTime      @updatedAt @map("updated_at") @db.Timestamptz(3)
+  session         AgentSession  @relation(fields: [sessionId], references: [id], onDelete: Cascade)
+  actions         AgentAction[]
+
+  @@unique([sessionId, clientMessageId])
+  @@index([sessionId, createdAt])
+  @@map("agent_messages")
+}
+
+model AgentAction {
+  id         String       @id @default(uuid()) @db.Uuid
+  messageId  String       @map("message_id") @db.Uuid
+  clientKey  String       @map("client_key")
+  type       String
+  status     String
+  moduleName String?      @map("module_name")
+  path       String?
+  command    String?
+  purpose    String?
+  reason     String?
+  content    String?
+  output     String?
+  exitCode   Int?         @map("exit_code")
+  error      String?
+  payload    Json?
+  sortOrder  Int          @default(0) @map("sort_order")
+  createdAt  DateTime     @default(now()) @map("created_at") @db.Timestamptz(3)
+  updatedAt  DateTime     @updatedAt @map("updated_at") @db.Timestamptz(3)
+  message    AgentMessage @relation(fields: [messageId], references: [id], onDelete: Cascade)
+
+  @@unique([messageId, clientKey])
+  @@index([messageId, sortOrder])
+  @@index([type, status, createdAt])
+  @@map("agent_actions")
+}