remove the list_containers and request_update_meta_inputs MCP tools

Both agent-facing tools go away end to end, with no replacement. This is
an intentional capability removal: agents can no longer enumerate their
own subtree, and can no longer queue a meta-flake input bump.

The system prompt and docs/tools/lifecycle.md land in this same commit
on purpose. A tool named in the prompt but absent from the server makes
agents confidently call something that doesn't exist, and the failure
then surfaces far from its cause.

Removed:

- MCP registrations and bodies (hive-agent-mcp), plus the now-unused
  UpdateMetaInputsArgs.
- Wire variants Request::ListDescendants,
  Request::RequestUpdateMetaInputs and Response::Containers, plus
  ContainerInfo, whose only consumer was that response.
- hive-c0re's handle_list_descendants (its whole module) and
  handle_request_update_meta_inputs, the two dispatch arms, and the
  require_group(agent, "approvals", ...) gate on the meta-inputs verb.
- The stream_enrich emoji entry and argument formatter.
- docs/tools/lifecycle.md (both tools it documented are gone), its two
  referrers, the tool-group tables and the agent-hierarchy prose.

Tool groups are kept, deliberately. ToolGroup::Lifecycle listed exactly
one tool and now lists none — it is vestigial, but the variant stays so
existing meta/capabilities.json grants still parse; retiring it is a
separate decision. ToolGroup::Approvals also listed exactly one tool,
but the group is NOT dead: check_can_cancel_approval still gates
cancel_loose_end's approval-cancel arm on it server-side.

ApprovalKind::UpdateMetaInputs stays too. Nothing in production code
produces it any more, but pre-existing approval rows may still carry it,
and the operator's own path to a meta update is unaffected — the
dashboard's POST /api/meta-update inserts the meta_update job directly,
bypassing approvals entirely.

The two format_ack tests in hive-agent-mcp that named
request_update_meta_inputs were only using it as a label string while
exercising the generic OkWarn/Ok renderer, so they are retargeted to a
surviving tool rather than deleted.

Note hive-c0re's priv_client::list_containers is a different thing (the
host-side privileged container listing behind hive-priv) and is
untouched.

Closes #4591

hive-c0re/src/socket_server/mod.rs

@@ -23,15 +23,12 @@ use tokio::task::JoinHandle;
 use crate::coordinator::Coordinator;
 
 mod config_approvals;
-mod lifecycle_handlers;
 mod schedules;
 
 pub(crate) use config_approvals::submit_merge_config_pr;
 pub(crate) use schedules::filter_ghost_schedule_targets;
 pub use schedules::schedule_to_wire_public;
 
-use config_approvals::handle_request_update_meta_inputs;
-use lifecycle_handlers::handle_list_descendants;
 use schedules::{
     EditSchedulePatch, handle_cancel_schedule, handle_edit_schedule, handle_fire_schedule_now,
     handle_list_schedules, handle_request_schedule_prompt,
@@ -181,9 +178,9 @@ pub(crate) fn recv_timeout(wait_seconds: Option<u64>) -> std::time::Duration {
 /// Handle the subset of `Request` variants that are identical on both
 /// the agent socket and the manager socket. Returns `Some(response)` for
 /// every variant it handles; returns `None` for the remaining variants —
-/// `ListDescendants` and the orchestration verbs (schedules / meta-inputs),
-/// which need per-verb tool-group gating — or for host-admin / unknown
-/// requests invalid on either socket.
+/// `GetLooseEnds` and the orchestration verbs (schedules), which need
+/// per-verb tool-group gating — or for host-admin / unknown requests
+/// invalid on either socket.
 ///
 /// The unified `dispatch` calls this first; the remaining arms (which gate
 /// on topology / capabilities / tool-groups) are handled there.
@@ -542,14 +539,13 @@ fn handle_requeue_inflight(
 /// Unified dispatch for every socket connection — per-agent sockets and the
 /// (now pure-transport) manager socket alike. There is no privilege bit;
 /// authority derives uniformly from the caller's identity: hive-wide
-/// orchestration verbs (schedules / meta-inputs) require the matching
-/// tool-group (the grantable capability).
+/// orchestration verbs (schedules) require the matching tool-group (the
+/// grantable capability).
 async fn dispatch(req: &Request, agent: &str, coord: &Arc<Coordinator>) -> Response {
     if let Some(resp) = dispatch_shared(req, agent, coord).await {
         return resp;
     }
     match req {
-        Request::ListDescendants => handle_list_descendants(coord, agent).await,
         Request::GetLooseEnds => handle_get_loose_ends(coord, agent),
         // Orchestration verbs — gated per-verb on tool-group membership
         // (see `dispatch_orchestration`).
@@ -557,21 +553,12 @@ async fn dispatch(req: &Request, agent: &str, coord: &Arc<Coordinator>) -> Respo
     }
 }
 
-/// Handle the hive-wide orchestration verbs (scheduling, meta-input updates).
-/// No blanket socket gate: each verb gates on the grantable capability that
-/// authorises it — the matching tool-group (`scheduling` / `approvals`). Any
-/// other variant is a host-admin / unknown request invalid on either socket.
+/// Handle the hive-wide orchestration verbs (scheduling). No blanket socket
+/// gate: each verb gates on the grantable capability that authorises it —
+/// the matching tool-group (`scheduling`). Any other variant is a
+/// host-admin / unknown request invalid on either socket.
 async fn dispatch_orchestration(req: &Request, agent: &str, coord: &Arc<Coordinator>) -> Response {
     match req {
-        Request::RequestUpdateMetaInputs {
-            inputs,
-            description,
-        } => {
-            if let Some(err) = require_group(agent, "approvals", "request update_meta_inputs") {
-                return err;
-            }
-            handle_request_update_meta_inputs(coord, agent, inputs, description.as_deref())
-        }
         Request::RequestSchedulePrompt(payload) => {
             if let Some(err) = require_group(agent, "scheduling", "schedule a prompt") {
                 return err;