Multiple /stream calls for same workflow runId create duplicate Inngest events, triggering multiple full workflow executions (e.g., parallel steps create 3x Zendesk tickets instead of 1). Duplicate side-effects despite same input/runId.

InngestRun._start() calls this.inngest.send() without event-level `id` (idempotency key), sending new Inngest events even for existing runId. Stream() guards fail across multiple /stream requests (new InngestRun instances). Idempotency option not forwarded to inngest.createFunction().