feat(core): add embedded v2 session runtime and tool foundation (#30632)

packages/core/src/session/error.ts

@@ -0,0 +1,8 @@
+import { Schema } from "effect"
+import { SessionMessage } from "./message"
+import { SessionSchema } from "./schema"
+
+export class MessageDecodeError extends Schema.TaggedErrorClass<MessageDecodeError>()("Session.MessageDecodeError", {
+  sessionID: SessionSchema.ID,
+  messageID: SessionMessage.ID,
+}) {}