Let a job choose its AMS slot; soak test for telemetry

POST /jobs takes an optional amsSlot (stored in the job metadata) which
dispatch passes to the gateway. The camera e2e script gains SOAK_S.

src/dispatch/index.ts

@@ -213,6 +213,8 @@ export async function dispatchTick(): Promise<number> {
         job_id: job.id,
         file_name: job.fileName,
         url,
+        // Chosen by whoever queued the job; absent means "by the project's filament".
+        ...(typeof job.metadata?.amsSlot === "number" ? { ams_slot: job.metadata.amsSlot } : {}),
       });
 
       if (!result.ok) {