Fix workflow state lost after Durable Object hibernation

Make requireInitialized() async so it can reload workflow state from the
database when the DO wakes from hibernation, instead of throwing an error.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bchapuis

apps/api/src/durable-objects/workflow-agent.ts

@@ -148,7 +148,7 @@ export class WorkflowAgent extends Agent<Bindings, WorkflowAgentState> {
     message: string | ArrayBuffer
   ): Promise<void> {
     try {
-      this.requireInitialized();
+      await this.requireInitialized();
 
       if (typeof message !== "string") {
         connection.close(1003, "Binary messages not supported");
@@ -265,21 +265,22 @@ export class WorkflowAgent extends Agent<Bindings, WorkflowAgentState> {
   }
 
   /**
-   * Throws if workflow state is not loaded. Used by onMessage which always
-   * runs after onConnect has loaded state — failure here means the DO
-   * woke from hibernation and Agent state was lost.
+   * Ensures workflow state is loaded. If the DO woke from hibernation and
+   * in-memory state was lost, attempts to reload from the database using
+   * the persisted Agent state.
    */
-  private requireInitialized(): void {
+  private async requireInitialized(): Promise<void> {
     if (this.workflowState) return;
 
     const { workflowId, userId } = this.state ?? {};
     if (!workflowId || !userId) {
       throw new Error("Session state lost. Please refresh the page.");
     }
-    // State exists in Agent storage but not loaded into memory yet.
-    // This shouldn't happen in practice since onConnect always loads first,
-    // but if it does, the throw above gives a clear error.
-    throw new Error("Workflow state not loaded. Reconnect to reload.");
+
+    // DO woke from hibernation — reload state from database
+    if (await this.tryLoadState(workflowId, userId)) return;
+
+    throw new Error("Failed to reload workflow state after hibernation.");
   }
 
   /**