Exercise the same-room collaboration acceptance fixture without a model #219

Next deterministic fixture slice of #198, alongside the DSH boundary in #216/#218. Use the actual FlyBot room relay and task channel with scripted DSH session events, not the separate offline transport simulator.

Acceptance:

• An isolated synthetic code task drives Chief → Writer delegation, a required Writer clarification in the room, Chief's answer, a real fixture code edit and test run, independent Chief verification, and requester-controlled result acceptance/rejection.
• Keep the fixture and independent assertions reusable for a later OpenCode driver; the verifier tests live outside the Writer workspace and actually execute against the returned artifact.
• A bad implementation can pass the Writer's narrow self-test but must fail independent verification and remain unaccepted. Reject acceptance before result-ready. Preserve message authorship, distinct room session identities and ordered clarification provenance.
• The test coordinator explicitly drives requester bookkeeping; this is not automatic task/session exchange wiring. Human acceptance is simulated, not a claim that a person reviewed a real model's work.
• Run deterministically without models, credentials, external traffic or a real OpenCode process. Full local verification and packaging gates must pass; document unexercised boundaries. Keep [RFC] 跨运行时 Agent 对话与协作：以 OpenCode 为首个试点的目标、需求与两种方案 #198 open.