Adds an optional sessionKey to the WakeParamsSchema and threads it through
the gateway wake handler, CronService.wake(), and the underlying timer.wake()
ops so callers can target a specific session for async-task completion
relays instead of always hitting the agent's main session.
Also adds --session-key to `openclaw system event`.
The schema rejects empty/non-string sessionKey at the gateway boundary;
mismatched session keys (a key that does not belong to the resolving agent)
fall back to the agent's main session inside resolveCronSessionKey, which
is the existing safety path.
Refs #52305 (companion to PR #50818, which closes the related cron-run
remap slice at internal enqueue sites). Doesn't depend on #50818.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
