Subagent No Report Channel

Recover the work of a spawned subagent that finished but never reported, and tell that case apart from a genuinely wedged agent. Use when: (1) subagents go idle repeatedly with no findings delivered, (2) `ListAgents` shows them alive but nothing ever arrives in your inbox, (3) an agent's own final text says the send tool was unavailable or disabled, (4) you spawned a restricted agent type (a wrapper that dispatches to a background job runtime) and it reports that polling status/result is outside its role, (5) you are about to kill and respawn agents because they "hung". Root cause: an agent type's declared toolset may not include a messaging tool, so a correct, completed …