- Promote HEARTBEAT_NO_TASK_SYSTEM_PROMPT as the primary no-task heartbeat constant while keeping a backward-compatible alias.
- Refine no-task heartbeat guidance for lightweight ambient coordination and explicit tool usage.
- Select the no-task prompt for heartbeat runs without task context before appending instruction/rating overlays.
- Update heartbeat regression tests to assert the renamed no-task prompt constant and prompt/tool expectations.
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