feat(core): API-managed per-session context entries (#34941)

packages/schema/src/session-context-entry.ts

@@ -0,0 +1,20 @@
+export * as SessionContextEntry from "./session-context-entry.js"
+
+import { Schema } from "effect"
+
+/**
+ * Slash-free client-facing key for one API-managed context entry. The server
+ * derives the namespaced SystemContext key as `api/<key>`, keeping the
+ * `api/*` namespace enforced by construction.
+ */
+export const Key = Schema.String.check(Schema.isPattern(/^[a-z0-9][a-z0-9._-]*$/)).annotate({
+  identifier: "SessionContextEntry.Key",
+  description: "Context entry key (lowercase alphanumerics plus . _ -)",
+})
+export type Key = typeof Key.Type
+
+export const Info = Schema.Struct({
+  key: Key,
+  value: Schema.Json.annotate({ description: "JSON value attached to the session's system context" }),
+}).annotate({ identifier: "SessionContextEntry.Info" })
+export interface Info extends Schema.Schema.Type<typeof Info> {}