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-agent/src/stream_enrich.rs

@@ -498,8 +498,7 @@ fn tool_icon(name: &str) -> &'static str {
         "mcp__hyperhive__cancel_loose_end" => "✂️",
         "mcp__hyperhive__ack_until" => "✅",
         "mcp__hyperhive__get_agent_meta" => "ℹ️",
-        "mcp__hyperhive__list_containers"
-        | "mcp__matrix__list_rooms"
+        "mcp__matrix__list_rooms"
         | "mcp__matrix__list_room_members"
         | "mcp__matrix__list_invites" => "📋",
         "mcp__hyperhive__get_host_journal" => "📜",
@@ -666,8 +665,7 @@ fn fmt_hyperhive_tool(name: &str, short: &str, input: &Value) -> String {
             }
         }
         "mcp__hyperhive__remind" => fmt_hyperhive_remind(short, input),
-        "mcp__hyperhive__request_update_meta_inputs"
-        | "mcp__hyperhive__list_schedules"
+        "mcp__hyperhive__list_schedules"
         | "mcp__hyperhive__cancel_schedule"
         | "mcp__hyperhive__fire_schedule_now"
         | "mcp__hyperhive__edit_schedule"
@@ -792,17 +790,6 @@ fn fmt_hyperhive_edit_schedule(short: &str, input: &Value) -> String {
 /// Schedule-management hyperhive tools (list/cancel/fire/edit/request).
 fn fmt_hyperhive_schedule_tool(name: &str, short: &str, input: &Value) -> String {
     match name {
-        "mcp__hyperhive__request_update_meta_inputs" => {
-            let ins = match input.get("inputs").and_then(Value::as_array) {
-                Some(arr) if !arr.is_empty() => {
-                    let names: Vec<&str> = arr.iter().filter_map(Value::as_str).take(4).collect();
-                    let tail = if arr.len() > 4 { ", …" } else { "" };
-                    format!("[{}{}]", names.join(", "), tail)
-                }
-                _ => "all".to_owned(),
-            };
-            format!("{short} {ins}")
-        }
         "mcp__hyperhive__list_schedules" => format!("{short}()"),
         "mcp__hyperhive__cancel_schedule" => {
             let id = input