docs: clarify projection initialization ordering

.agents/skills/dsh-session-projection/SKILL.md

@@ -16,3 +16,4 @@ Follow the [projection API](../../../packages/session/session-projection/README.
 7. After migrating to Session persistence, stop using `fold` in names and descriptions of the migrated logic.
 8. Do not add calls to deprecated synchronous readers (`snapshotEvents`, `eventAt`, `ownEvents`) or wrappers exposing the same access ([decision](../../notes/implemented/architecture/2026-09-09-deprecate-synchronous-session-event-reads.md)). Assume the full event log is not resident in memory and random reads may require asynchronous disk access.
 9. Consider state size, replay cost, and per-event work; add complexity only for a concrete performance need.
+10. Asynchronous `register()` is usually called in `[Service.init]`. If event listeners are registered afterward, check initialization ordering: when needed, install listeners before awaiting registration; if a listener needs the returned handle, await its readiness in a callback that supports asynchronous waiting. Otherwise, an event may fire before the listener is installed and be missed. Determine whether this race exists from the actual initialization flow and event trigger paths; do not move listeners earlier or add waits mechanically.