Prevent Pi from rejecting accepted prompts

[evaera]

Paseo already decides whether input should interrupt, steer, or wait in the Queue track. That behavior is unchanged.

Once Paseo sends a prompt, Pi requires an explicit streaming behavior if it still considers the session busy. Without one, an accepted prompt can fail with “Agent is already processing.”

This sends Paseo’s steering path as steer and ordinary accepted prompts as followUp, while leaving client-side queueing and interruption behavior intact.

[boudra]

Closing for now: this needs a before/after reproduction against real Pi showing an accepted prompt rejected while busy and then handled correctly, with the Pi version recorded. Please reopen with that evidence.

[boudra]

Please disregard the earlier invitation to reopen with evidence. This PR remains closed unless I explicitly follow up. You don't need to resubmit this PR or provide further QA evidence.

Please read the updated PR policy. For now, I'm automatically closing feature PRs so I can focus more time on bug fixes and core improvements. Focused bug-fix PRs with a clear reproduction and QA are still welcome. The previous guide already asked contributors to submit only if they were comfortable with closure, and explained that unsolicited PRs could be closed without a detailed review.

For feature ideas, please start in GitHub Discussions and share your workflow: what you're trying to do, how you do it today, and where Paseo gets in the way. If there's already a discussion about it, join in and share your use case. I'll periodically review discussions for highly requested workflows and use that feedback to shape the roadmap.

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There are hundreds of PRs alongside ongoing development. I can't commit to reviewing every submission, providing individual feedback or giving timelines.