fix(review): drop libnull.rlib artifact + add Errors doc to ensure_config_pr_webhook

- Remove libnull.rlib accidentally committed in previous push (cargo
  check --no-default-features side-effect); add *.rlib to .gitignore
  to prevent recurrence
- Add # Errors section to ensure_config_pr_webhook doc comment
  (argus: missing on pub async fn returning Result<()>)

hive-c0re/src/forge/mod.rs

@@ -307,6 +307,18 @@ pub async fn ensure_all() {
 ///
 /// Called at startup alongside `knowledge::ensure_webhook`. No-op when the
 /// core token is absent (forge not yet provisioned).
+///
+/// # Errors
+///
+/// Returns an error if:
+/// - `dashboard_port` produces a URL that `url::Url::parse` rejects (should
+///   never happen for a valid port number).
+/// - The Forgejo `org_create_hook` API call fails (transport error, auth
+///   failure, or the `agent-configs` org does not exist).
+/// - The HTTP call times out (10 s limit).
+///
+/// Listing failures are treated as best-effort: they fall through to the
+/// create attempt rather than surfacing an error.
 pub async fn ensure_config_pr_webhook(core_token: &str, dashboard_port: u16) -> Result<()> {
     use forgejo_api::structs::{CreateHookOption, CreateHookOptionConfig, CreateHookOptionType};
     use std::collections::BTreeMap;