fix(api): completedAt: null on non-complete states + OpenAPI timestamps & rate-limit headers (#29)

artifacts/api-server/src/routes/jobs.ts

@@ -309,6 +309,7 @@ router.get("/jobs/:id", async (req: Request, res: Response) => {
       jobId: job.id,
       state: job.state,
       createdAt: job.createdAt.toISOString(),
+      completedAt: job.state === "complete" ? job.updatedAt.toISOString() : null,
     };
 
     switch (job.state) {
@@ -356,7 +357,6 @@ router.get("/jobs/:id", async (req: Request, res: Response) => {
       case "complete":
         res.json({
           ...base,
-          completedAt: job.updatedAt.toISOString(),
           result: job.result ?? undefined,
           ...(job.actualCostUsd != null ? {
             costLedger: {