docs: replace vague provenance prose with recorded facts

packages/subagent/tool-subagent-control/README.md

@@ -4,7 +4,7 @@ English | [中文](README.zh.md)
 
 The optional, globally named `send_message`, `interrupt_agent`, and `list_agents` tools are thin adapters over `ctx.subagents`. Provider-bound `@deepseek-ai/dsh-tool-subagent` instances register distinct delegation tools per transport; this separately loaded package registers shared control tools once, so multiple delegation tools never register duplicate global controls. The root plugin registers `send_message` and `interrupt_agent` and requires only `subagents`; the separately loadable `./list-agents` plugin registers `list_agents` and declares `subagents` plus `agents` as load-time dependencies. Its catalog reads additionally require the session store and projection registry at call time, but no query service. A deployment can keep the root tools while omitting the list tool. No tool's presence determines whether a delegation tool starts continuable work. These tools own only the parent-to-child direction; the independently installed [`@deepseek-ai/dsh-tool-subagent-report`](../tool-subagent-report/README.md) owns the child-to-parent direction.
 
-The tool performs no lifecycle routing — residency and cold resume belong to the subagent service. It passes `exec.agent` as the exact live parent that authorizes delivery and attributes every message as durable provenance `{ kind: 'coordinator', senderSessionId: parent.id }`, which the service retains but never treats as authority. Every message becomes the subagent's next FIFO turn through `Agent.followup()`: if the child is still working, the message waits until its current turn finishes, so it cannot redirect work already underway. The tool forwards its execution signal, which owns admission only until inbox acceptance; once the child accepts the message the accepted turn cannot be cancelled through this tool. This call returns no child reply — its transcript by that id is the source of what it did — and a child with `report` sends content on its own initiative as a separate parent message. A delivery failure becomes an errored tool result stating the message was not delivered.
+The tool performs no lifecycle routing — residency and cold resume belong to the subagent service. It passes `exec.agent` as the exact live parent that authorizes delivery and records every message source as `{ kind: 'coordinator', senderSessionId: parent.id }`, which the service retains but never treats as authority. Every message becomes the subagent's next FIFO turn through `Agent.followup()`: if the child is still working, the message waits until its current turn finishes, so it cannot redirect work already underway. The tool forwards its execution signal, which owns admission only until inbox acceptance; once the child accepts the message the accepted turn cannot be cancelled through this tool. This call returns no child reply — its transcript by that id is the source of what it did — and a child with `report` sends content on its own initiative as a separate parent message. A delivery failure becomes an errored tool result stating the message was not delivered.
 
 `interrupt_agent(agent_id)` passes `exec.agent` as the exact live ancestor authority for `ctx.subagents.interrupt()`: the target may be a direct child or a deeper descendant, and the service — never this tool — verifies the caller against the target Activation's recorded lineage. Only the target's current turn stops (`keepInbox`): queued messages stay parked until a later `send_message`, published descendants keep running, and the child stays available for follow-ups. The call returns as soon as the stop request is accepted, without waiting for target quiescence; an absent or already-settled target is an accepted no-op, while self, sibling, stale, and non-ancestor callers become errored results.