Pause a Trigger.dev v4 run with wait.for/wait.until and run subtasks with triggerAndWait without burning compute

Documented steps

1. Import from the v4 SDK: `import { task, wait } from "@trigger.dev/sdk";` (https://trigger.dev/docs/wait).
2. For a fixed delay call `await wait.for({ seconds: 5 })` — units are seconds, minutes, hours, days, weeks, months, years (https://trigger.dev/docs/wait-for).
3. To resume at an instant call `await wait.until({ date: new Date(payload.date) })`, optionally with `throwIfInThePast: true` (https://trigger.dev/docs/wait-until).
4. To run a subtask and block on it: `const result = await childTask.triggerAndWait(payload);` then check `result.ok` before reading `result.output`, or call `.unwrap()` to get the output directly and throw on failure.
5. For parallel subtasks use `await childTask.batchTriggerAndWait(items)` rather than `Promise.all()` of individual triggerAndWait calls.
6. Make waits retry-safe by passing `idempotencyKey` (and optionally `idempotencyKeyTTL`) to `wait.for`/`wait.until`.
7. Rely on the documented checkpoint behavior: waiting on a subtask trigger checkpoints the parent and does not count toward compute usage; time-based waits longer than 5 seconds are also checkpointed and excluded from compute usage.