prompts+docs: the lifecycle tools reach the whole subtree, not just direct children

`require_descendant` (`socket_server/mod.rs:666`) authorises
kill/start/restart/update/get_logs with `topology::is_descendant_of` — the
caller's whole subtree, itself included. That has been true since `53b4e752`
(#1865), whose message says "a parent owns its whole subtree; the root covers
every agent as a consequence, no positional privilege", and two tests pin it
(`is_descendant_of_in_grandchild`, `is_descendant_of_in_self_is_true`).

The prose never followed. The four lifecycle tool descriptions, their
`// IMPORTANT:` comments, `docs/tools/lifecycle.md`, the tools README,
hive-agent-mcp's README and the system prompt every agent is rendered from all
still said "direct children only" — while `list_containers`, four tools away in
the same file, said "direct children + their subtrees".

`lifecycle.md` also taught the model #1865 deleted: "Privileged agents (for
example ruth) may operate on any sub-agent — the topology scope applies to all
others." There is no privileged class to belong to; ruth reaches every agent
because the check is transitive and everything sits under it.

Same drift on the state-query side: `resolve_agent_state_target` is
subtree-scoped by the same commit, so `get_loose_ends`' argument doc, the
`QueryAgentState` capability doc and `docs/turn-loop/mcp.md` were all telling a
parent it needs a capability to read a grandchild's threads.

Two smaller corrections found on the way:

* `list_containers` returns the caller itself. `is_descendant_of` is true for
  `candidate == ancestor` and `handle_list_descendants` filters the topology
  with it; called from a leaf agent it answers one row, that agent.
* `request_init_config` accepts any unused name — the requester becomes its
  parent — or an existing agent already in the caller's subtree, not "a direct
  child". The editing surface is narrower than the guard, though: only direct
  children's config repos are bind-mounted, so re-seeding deeper in the subtree
  leaves no local copy to edit. `lifecycle.md` now says so.

The prompt's other stale claim, the dead `request_apply_commit`, is #4226 and
was fixed independently by damocles in #4227 while this was being gated. This
branch keeps only the scope wording on that line.

Closes #4225.

docs/tools/lifecycle.md

@@ -1,14 +1,15 @@
 # Lifecycle and approvals tools
 
 Two tool groups govern agent lifecycle management and config changes.
-The server scopes both to **direct children only** (topology-enforced: it
-rejects any name that's not a direct child of the calling
-agent per `topology.json`). Privileged agents (for example ruth) may operate
-on any sub-agent — the topology scope applies to all others.
+The server scopes both to the caller's **own subtree** (topology-enforced
+per `topology.json`: a child, a child's child, every agent below them —
+plus the caller itself). No privileged class exists to belong to; the
+root agent reaches every agent purely because the check is transitive and
+everything sits under it.
 
 ## `lifecycle` tool group
 
-No operator approval required. Direct children only.
+No operator approval required. The caller's own subtree.
 
 ### `kill(name)`
 
@@ -31,17 +32,19 @@ to `needs_update` system events.
 
 ### `list_containers()`
 
-List all **descendant** containers (children + their subtrees) with
-running status. Topology-scoped to descendants only.
+List the caller's whole **subtree** with running status — children,
+their children, every agent below them. The calling agent is part of its
+own subtree, so it appears in its own listing; a leaf agent gets a
+one-row answer naming itself.
 
 ## `approvals` tool group
 
 Config changes and new-agent spawns route through the operator
-approval queue. Direct children only (topology-enforced).
+approval queue. Topology-enforced the same way.
 
 ### `request_init_config(name, description?)`
 
-Step 1 of spawning a new direct child agent. Queues an `InitConfig`
+Step 1 of spawning a new sub-agent. Queues an `InitConfig`
 approval; on operator approve, hive-c0re seeds the proposed config
 repo at `/agents/<name>/config/agent.nix` with a default template and
 delivers a `config_ready` system event. Then edit `agent.nix`, commit,
@@ -54,6 +57,17 @@ Subsequent config changes go through a **forge PR** on the agent's
 open/update — no MCP tool involved), not a tool call. See
 `docs/agent-lifecycle/approvals.md`.
 
+`name` must be either unused — in which case the caller becomes its
+parent on approval — or an agent already in the caller's subtree whose
+config is being re-seeded. The server refuses a name that exists outside
+that subtree, so one agent can't hijack another's.
+
+Only **direct** children's config repos are bind-mounted into a parent's
+container, though (`bind_child_agent_dirs`, driven by
+`topology::children_of`). The server accepts re-seeding an agent further
+down the subtree, and that still leaves the caller without a local copy
+to edit afterwards.
+
 Fails if a proposed config repo for `name` already exists.
 `name` is ≤ 9 characters.
 
@@ -69,12 +83,12 @@ agents after the approval resolves.
 
 ## Boundary summary
 
-| Operation                               | Requires approval? | Scope                 |
-| --------------------------------------- | ------------------ | --------------------- |
-| `kill` / `start` / `restart` / `update` | No                 | Direct children       |
-| `list_containers`                       | No                 | All descendants       |
-| `request_init_config`                   | Yes (InitConfig)   | New direct child only |
-| `request_update_meta_inputs`            | Yes (MetaUpdate)   | Meta flake (global)   |
+| Operation                               | Requires approval? | Scope                              |
+| --------------------------------------- | ------------------ | ---------------------------------- |
+| `kill` / `start` / `restart` / `update` | No                 | Own subtree                        |
+| `list_containers`                       | No                 | Own subtree, caller included       |
+| `request_init_config`                   | Yes (InitConfig)   | Unused name, or one in own subtree |
+| `request_update_meta_inputs`            | Yes (MetaUpdate)   | Meta flake (global)                |
 
 ## See also