feat(proxy): add agent/session/run Prisma models

Add 4 new tables for the agent_session_endpoints module (Cursor SDK on LiteLLM):

- LiteLLM_Agent: agent definition (model, system prompt, default repos)
- LiteLLM_AgentSession: VM-backed conversation owned by an agent
- LiteLLM_AgentRun: single turn within a session
- LiteLLM_AgentRunEvent: append-only event log for resumable SSE

Includes cascade deletes, idempotency unique constraints, and indexes
for the cleanup sweeper and ownership lookups.

schema.prisma

@@ -1374,3 +1374,97 @@ model LiteLLM_WorkflowMessage {
   @@unique([run_id, sequence_number])
   @@index([run_id])
 }
+
+
+// ===========================================================================
+// Agent Sessions / Runs (Cursor SDK on LiteLLM)
+//
+// Three-level hierarchy:
+//   Agent      — definition (model, system prompt, default repos, tools)
+//   Session    — VM-backed conversation, owned by an Agent
+//   Run        — single turn within a Session
+//   RunEvent   — append-only event log per run (for resumable SSE)
+// ===========================================================================
+
+model LiteLLM_Agent {
+  id                String   @id  // "agent_<uuid>"
+  name              String
+  user_api_key_hash String
+  team_id           String?
+  model             String
+  system_prompt     String?
+  default_repos     Json?
+  default_env_vars  Json?
+  tools_config      Json?
+  metadata          Json?
+  created_at        DateTime @default(now())
+  updated_at        DateTime @updatedAt
+
+  sessions LiteLLM_AgentSession[]
+
+  @@index([user_api_key_hash])
+  @@index([team_id])
+}
+
+model LiteLLM_AgentSession {
+  id                String   @id  // "sess_<uuid>"
+  agent_id          String
+  user_api_key_hash String
+  team_id           String?
+  vm_id             String?
+  vm_provider       String?
+  repos             Json
+  env_vars          Json?
+  status            String   @default("provisioning")
+  daemon_token_hash String?
+  expires_at        DateTime
+  last_heartbeat_at DateTime?
+  idempotency_key   String?
+  created_at        DateTime  @default(now())
+  updated_at        DateTime  @updatedAt
+  terminated_at     DateTime?
+
+  agent LiteLLM_Agent     @relation(fields: [agent_id], references: [id], onDelete: Cascade)
+  runs  LiteLLM_AgentRun[]
+
+  @@unique([user_api_key_hash, idempotency_key])
+  @@index([agent_id])
+  @@index([status, expires_at])
+  @@index([user_api_key_hash])
+}
+
+model LiteLLM_AgentRun {
+  id              String   @id  // "run_<uuid>"
+  session_id      String
+  parent_run_id   String?
+  status          String   @default("queued")
+  prompt          Json
+  result          String?
+  git_branches    Json?
+  idempotency_key String?
+  created_at      DateTime  @default(now())
+  updated_at      DateTime  @updatedAt
+  started_at      DateTime?
+  terminated_at   DateTime?
+
+  session LiteLLM_AgentSession   @relation(fields: [session_id], references: [id], onDelete: Cascade)
+  events  LiteLLM_AgentRunEvent[]
+
+  @@unique([session_id, idempotency_key])
+  @@index([session_id, status])
+  @@index([session_id, created_at])
+}
+
+model LiteLLM_AgentRunEvent {
+  id         String   @id @default(uuid())
+  run_id     String
+  seq        Int
+  event_type String
+  payload    Json
+  created_at DateTime @default(now())
+
+  run LiteLLM_AgentRun @relation(fields: [run_id], references: [id], onDelete: Cascade)
+
+  @@unique([run_id, seq])
+  @@index([run_id, seq])
+}