refactor(#2352): quota enable/limit via daemon wire commands

hive-c0re/src/server.rs

@@ -199,6 +199,8 @@ async fn dispatch(req: &HostRequest, coord: Arc<Coordinator>) -> HostResponse {
             HostRequest::SetAgentGithubToken { agent, token } => {
                 handle_set_agent_github_token(agent, token).await?
             }
+            HostRequest::QuotaEnable => handle_quota_enable().await?,
+            HostRequest::QuotaLimit { name, limit } => handle_quota_limit(name, *limit).await?,
         })
     }
     .await;
@@ -408,6 +410,25 @@ async fn handle_set_agent_github_token(agent: &str, token: &str) -> Result<HostR
     )]))
 }
 
+async fn handle_quota_enable() -> Result<HostResponse> {
+    crate::priv_client::ensure_btrfs_quota()
+        .await
+        .context("enable btrfs qgroup accounting")?;
+    Ok(HostResponse::messages(vec![
+        "btrfs qgroup accounting enabled on the agent-state filesystem.".to_owned(),
+        "(usage may read 0 until btrfs finishes its background rescan)".to_owned(),
+    ]))
+}
+
+async fn handle_quota_limit(name: &str, limit: Option<u64>) -> Result<HostResponse> {
+    crate::priv_client::set_subvolume_quota(name, limit)
+        .await
+        .with_context(|| format!("set quota for {name}"))?;
+    // Bare success: the client prints the human-readable confirmation from
+    // the value it sent (it holds the `human_bytes` formatter).
+    Ok(HostResponse::success())
+}
+
 async fn handle_matrix_sync_admin() -> Result<HostResponse> {
     require_matrix_present().await?;
     let register_token =