fix(ci): serialize env-mutating OAuth wildcard tests with ENV_MUTEX (#1280) (#1468)

Replace `unwrap_or_else(|e| e.into_inner())` with `expect("env mutex poisoned")`
in bind_rejects_wildcard_ipv4 and bind_rejects_wildcard_ipv6 tests to match the
ENV_MUTEX pattern used in oauth_defaults.rs. The old pattern silently recovered
from a poisoned mutex, potentially allowing concurrent env var access when a
prior test panicked while holding the lock.

[skip-regression-check]

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

src/llm/oauth_helpers.rs

@@ -390,7 +390,7 @@ mod tests {
     #[allow(clippy::await_holding_lock)]
     #[tokio::test]
     async fn bind_rejects_wildcard_ipv4() {
-        let _guard = ENV_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
+        let _guard = ENV_MUTEX.lock().expect("env mutex poisoned");
         let original = std::env::var("OAUTH_CALLBACK_HOST").ok();
         // SAFETY: Under ENV_MUTEX, no concurrent env access.
         unsafe { std::env::set_var("OAUTH_CALLBACK_HOST", "0.0.0.0") };
@@ -414,7 +414,7 @@ mod tests {
     #[allow(clippy::await_holding_lock)]
     #[tokio::test]
     async fn bind_rejects_wildcard_ipv6() {
-        let _guard = ENV_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
+        let _guard = ENV_MUTEX.lock().expect("env mutex poisoned");
         let original = std::env::var("OAUTH_CALLBACK_HOST").ok();
         // SAFETY: Under ENV_MUTEX, no concurrent env access.
         unsafe { std::env::set_var("OAUTH_CALLBACK_HOST", "::") };