[Fix] Fast mode sends inconsistent chat updates

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote or in the web UI.

What changed

• Extracted the provider-aware chat response lifecycle into one policy shared by sandbox task workflows and Fast mode.
• Aligned Fast mode with the task-side rules for immediate responses, acknowledgements, decision-useful progress, clarifications, fresh responses, and single terminal closeouts.
• Preserved Fast-specific orchestration for queued acknowledgements and progress, automatic Brain preflight, parent-owned task kickoffs, integration calls, and delegated-task platform events.
• Tightened platform events so routine events can remain silent and useful events can only post a terminal closeout, never an orphaned clarification.
• Added focused coverage for direct responses, silent events, visible acknowledgement/progress ordering, clarification rejection, and closeout behavior.

Why this change was made

Fast mode maintained a separate condensed copy of the chat response rules, which could drift from the canonical task-side behavior. Sharing the decision policy keeps the two execution paths consistent without coupling Fast mode to sandbox-only orchestration.

Impact

Fast conversations now follow the same response-frequency and lifecycle decisions as sandbox tasks. Immediate answers avoid redundant acknowledgements, longer work reports only useful progress, every directed human turn receives a fresh response, and delegated-task events either produce one useful closeout or stay silent.

[roomote-community]

No code issues found. See task

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