hivectl, docs: choom is not root-only, and set-limits takes no agent name

Two unrelated changes landed correctly and left their prose behind, both
on operator-facing surfaces.

`hivectl agent <name> choom` gained a `hive-admin` path when hive-c0re
started shipping a polkit rule for `machinectl shell`. `choom.rs`
implements exactly that — `euid != 0 && !in_hive_admin_group()` — but
the `Choom` variant's clap doc comment still said "Requires root and a
running container", eight weeks on. That string is what
`choom --help` prints and what renders into the generated CLI
reference, so it is the sentence an operator actually reads, and it
tells a `hive-admin` member the command is not available to them.
`docs/turn-loop/mcp.md` carried the same staleness inside a
trust-boundary argument ("an operator (root) action"), where naming a
narrower reachable set than the real one is the wrong way to be wrong.

Dating it rather than asserting it: the acceptance landed 2026-09-07,
the doc string 2026-07-16.

Separately, `docs/tools/hivectl.md` states the agent-name hoist itself
("the name is hoisted onto the parent command, so none of the verbs
below repeat it") and its own example block obeys it, then twice writes
`set-limits sock --memory-max 8G` — the pre-hoist order. The generated
reference is unambiguous: `hivectl agent <NAME> <COMMAND>` versus
`hivectl agent set-limits [OPTIONS]`, with `quota set <SIZE>` nearby
showing that positionals do render when they exist. The costly one is a
complete command in backticks inside the paragraph explaining the
footgun it illustrates.

`docs/tools/hivectl-cli.md` is regenerated rather than hand-edited; the
diff against the committed copy is exactly one line.

Closes #4236.

hivectl/src/cli.rs

@@ -544,7 +544,7 @@ pub enum AgentCmd {
     /// Open an interactive Claude session inside this agent's container.
     ///
     /// A fresh session by default, or resume a prior one. Requires root
-    /// and a running container.
+    /// or `hive-admin` group membership, plus a running container.
     Choom {
         /// Resume a prior claude session by its session id, passed
         /// through as `claude --resume <value>` (claude's `--continue`