hive-c0re: remove the approvals subsystem

Nothing submits an approval since scheduled prompts left hive-c0re, so the
queue only acted on rows written before that.

- hive-c0re: the approvals store and its migrations, approve/deny/
  resolve actions, the ResolveApproval tail node (and meta_update's
  approval_id), POST /api/approve and /api/deny, the approval views on
  /api/state, the approval_resolved dashboard event, the orphan GC,
  destroy/purge failing pending rows, and the approval rows in
  get_loose_ends. DestroyBookkeeping loses the purge flag, which only
  worded the approval-failure note.
- The CancelLooseEnd request goes: its only hive-c0re arm was the
  approval one. cancel_loose_end handles reminder and todo in the harness.
- Wire types: hive_sh4re::approvals (ReminderStats moves to inbox),
  LooseEnd::Approval, CancelLooseEndKind, HelperEvent::ApprovalResolved,
  ToolGroup::Approvals, HostRequest::{Pending,Approve,Deny} and
  HostResponse.approvals. HOST_SOCK_VERSION goes to 2 for the removed
  field.
- hivectl loses the approvals verbs; docs/tools/hivectl-cli.md is
  regenerated.
- The system prompt drops approval_resolved.
- The approvals table stays in broker.sqlite, unread, the same way the
  operator_questions table was left when its store was removed.
- An `approvals` entry still in tool-groups.json is skipped with a warning
  by ToolGroup::parse_list, like any unknown group.
- docs/agent-lifecycle/approvals.md is renamed to config-changes.md so the
  code's doc pointers resolve; its content follows in the docs commit.

hive-c0re/src/server.rs

@@ -184,15 +184,6 @@ async fn dispatch(req: &HostRequest, coord: Arc<Coordinator>) -> HostResponse {
             // federation peer-config block) and open the web surfaces
             // (`hivectl open`).
             HostRequest::Urls => HostResponse::urls(hive_urls()),
-            HostRequest::Pending => HostResponse::pending(coord.approvals.pending()?),
-            HostRequest::Approve { id } => {
-                actions::approve(&coord, *id)?;
-                HostResponse::success()
-            }
-            HostRequest::Deny { id } => {
-                actions::deny(&coord, *id, None)?;
-                HostResponse::success()
-            }
             HostRequest::SetResourceLimits {
                 name,
                 cpu_quota,
@@ -342,7 +333,7 @@ async fn stream_agent_status(
                 write_response(&mut write, &HostResponse::agent_statuses(vec![row])).await?;
             }
             // Every other event kind on this channel is dashboard-only
-            // (approvals, broker traffic, the queue, …) — nothing this
+            // (broker traffic, the queue, …) — nothing this
             // subscriber asked for.
             Ok(_) => {}
             // Best-effort, same contract the dashboard's own live channel