feat(core): admit v2 skill guidance (#30843)

packages/core/src/session/sql.ts

@@ -11,7 +11,8 @@ import type { SessionSchema } from "./schema"
 import type { MessageID, PartID, SessionV1 } from "../v1/session"
 import { WorkspaceV2 } from "../workspace"
 import { Timestamps } from "../database/schema.sql"
-import type { SystemContext } from "../system-context"
+import type { SystemContext } from "../system-context/index"
+import { AgentV2 } from "../agent"
 
 type SessionMessageData = Omit<(typeof SessionMessage.Message)["Encoded"], "type" | "id">
 type V1MessageData = Omit<SessionV1.Info, "id" | "sessionID">
@@ -169,6 +170,7 @@ export const SessionContextEpochTable = sqliteTable("session_context_epoch", {
     .primaryKey()
     .references(() => SessionTable.id, { onDelete: "cascade" }),
   baseline: text().notNull(),
+  agent: text().$type<AgentV2.ID>().notNull().default(AgentV2.defaultID),
   snapshot: text({ mode: "json" }).notNull().$type<SystemContext.Snapshot>(),
   baseline_seq: integer().notNull(),
   replacement_seq: integer(),