Codex review on PR #78687 [P3] flagged that the docs say next-heartbeat
"waits for the next scheduled tick" while the patched timer collapses
next-heartbeat+sessionKey to an immediate targeted wake. Add a callout
describing the exception and pointing callers who want delayed delivery
back at the no-session-key path.
Refs #78687.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>