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/README.md

@@ -38,9 +38,9 @@ debug agent behavior.
 - **[forge-cli](forge-cli.md)** — the exhaustive, autogenerated
   flag-by-flag reference for `hive-forge`, kept in lockstep with the
   binary by CI the same way `hivectl-cli.md` is.
-- **[lifecycle](lifecycle.md)** — kill/start/restart/update for an
-  agent's own direct children, plus the approval-gated config-change
-  tools.
+- **[lifecycle](lifecycle.md)** — kill/start/restart/update for the
+  agents in a caller's own subtree, plus the approval-gated
+  config-change tools.
 - **[matrix](matrix.md)** — the matrix MCP tool surface
   (`mcp__matrix__*`) for agents with a matrix account, multiple
   accounts per agent, and declaring extra MCP servers generally.