list_children does not describe the load/openForMs/stalled fields it returns #733

What happens

list_children returns load for every child and, since #624/#696, openForMs and stalled when a child's oldest turn is old. The tool's description does not say so:

• plugins/tree/src/tools.js:78 — 'List your direct child bots (id, name, role). These and your parent are the only bots you can message.'
• the output at plugins/tree/src/tools.js:90-97 — load: tree.loadOf(id), openForMs above 0, stalled: true at or past STALLED_AFTER_MS.

A model reads the description, not the implementation: it does not learn that the answer tells it who is busy, how long a turn has been open, or that stalled exists at all. docs/subsystems/tree.md already documents the fields, so only the agent-facing surface is behind.

What should happen

The list_children description names the routing fields it returns, in the same voice as the existing sentence, for example:

List your direct child bots (id, name, role, and — when they are busy — load, openForMs, stalled). These and your parent are the only bots you can message. A child whose oldest open turn is old says so; send new work to an idle child first.

Exact wording is the implementer's, but it must mention load, openForMs and stalled and say what stalled means, and it must not promise a field the tool does not return.

Acceptance

• plugins/tree/test/tree.test.js (or the tools test that asserts descriptions) gains a case: the registered list_children description contains load, openForMs and stalled, and the tool's output schema still returns those keys.
• Red without the source change: restore the old description → the case fails on openForMs.
• node --test plugins/tree/test/*.test.js green; changelog fragment added.

Out of scope

No change to what the tool computes or returns; no core change.

Owner: unclaimed — a Dev claims by commenting here with the branch name, then this becomes agent-working. One issue, one pull request.

Written-by: Triage