Summary

Add a small self_nudge(delay_seconds, note?) tool for gateway sessions.

This arms a one-shot in-memory timer that later injects a hidden follow-up turn back into the same session. It gives the agent an easy way to check back on something later without creating a cron job.

Why

Right now the closest workaround is cron, which is heavier than needed for short-lived follow-up work and easier to misuse.

Typical case:

• the agent kicks off some work or waits for an external state change
• it replies to the user normally
• it arms a one-shot self-nudge for a later check
• when the timer fires, Hermes injects a hidden turn so the agent can continue

Expected behavior

• one active self-nudge per session; re-arming replaces the previous one
• the timer fires once and is then removed
• if a real user message arrives first, the nudge is cancelled
• if the model wants no visible reply for that turn, it can respond with NO_REPLY
• private reminder text should not leak through persisted tool-call arguments

Scope

This is meant for messaging/gateway sessions, not the API server and not a full cron replacement.