docs: add # Errors doc to ensure_hive_space

hive-c0re/src/matrix.rs

@@ -652,6 +652,11 @@ pub fn read_admin_token() -> Result<String> {
 ///
 /// The Space is a private `m.space` room owned by `@hive`. All agents
 /// are invited after their accounts are provisioned in [`ensure_all`].
+///
+/// # Errors
+///
+/// Returns an error if the Matrix homeserver is unreachable, the
+/// `createRoom` call fails, or the room-ID file cannot be written.
 pub async fn ensure_hive_space(
     client: &reqwest::Client,
     admin_token: &str,