Support steering in dispatch()

[danthegoodman1]

RFC

Summary

Support steering with agents

Background & Motivation

Right now, it seems like dispatch() only allows follow-up-like behavior, meaning you cannot provide more context to an agent while it's working. This is useful beyond watching an agent: if you've already dispatched something, but want to tell it to abort or enlighten it with something you've just remembered, then steering is the solution.

I would like to test this for production agents, but we require steering behavior.

Goals

• Support steering behavior for the agent

Example

Dispatch can take a mode: "steer" or similar. It's already supported by the pi harness, so this should mostly be about drilling the message IIUC.