* fix(cron): eliminate double-announce and replace delivery polling with push-based flow
- Set deliveryAttempted=true in announce early-return paths (active-subagent
suppression and stale-interim suppression) so the heartbeat timer no longer
fires a redundant enqueueSystemEvent fallback (double-announce bug).
- Refactor waitForDescendantSubagentSummary to use event-based agent.wait RPC
calls instead of a 500ms busy-poll loop. Each active descendant run is now
awaited concurrently via Promise.allSettled, and only a short bounded grace
period (5s) remains to capture the cron agent's post-orchestration synthesis.
Eliminates O(n*timeoutMs/500ms) gateway calls and wasted wall-clock time.
- Add FAST_TEST_MODE (OPENCLAW_TEST_FAST=1) to subagent-followup.ts to keep
the grace-period tests instant in CI.
- Add comprehensive tests for the new waitForDescendantSubagentSummary behaviour
(push-based wait, error resilience, NO_REPLY handling, multi-descendant waits).
* fix: prep cron double-announce followup tests (#39089) (thanks @tyler6204)
e554c59aac