feat(schedule): add durable after package

packages/schedule/tool-schedule/src/persistence.ts

@@ -0,0 +1,31 @@
+/** Schedule-owned use of the shared session durability barrier. */
+
+import type { Context } from 'cordis'
+import type { Session } from '@deepseek-ai/dsh-session'
+
+/** Failure to prove that the current live prefix reached a persistence listener. */
+export class SchedulePersistenceError extends Error {
+  /**
+   * Construct a contained persistence failure.
+   * @param cause - Rejection returned by the shared barrier, when present.
+   */
+  constructor(cause?: unknown) {
+    super('Schedule persistence did not complete.', cause === undefined ? undefined : { cause })
+    this.name = 'SchedulePersistenceError'
+  }
+}
+
+/**
+ * Require one successful shared persistence checkpoint.
+ * @param ctx - Context carrying the live session store.
+ * @param session - Exact live session to checkpoint.
+ * @returns After at least one listener explicitly acknowledges completed durability work.
+ */
+export async function flushSchedulePersistence(ctx: Context, session: Session): Promise<void> {
+  try {
+    if (!await ctx.sessions.flush(session)) throw new SchedulePersistenceError()
+  } catch (error: unknown) {
+    if (error instanceof SchedulePersistenceError) throw error
+    throw new SchedulePersistenceError(error)
+  }
+}