fix(auth): address CodeRabbit review feedback on OAuth UX

Made-with: Cursor

src/auth/openai_oauth.rs

@@ -298,8 +298,9 @@ pub fn parse_code_from_redirect(input: &str, expected_state: Option<&str>) -> Re
         if let Some(got) = params.get("state") {
             if got != expected_state {
                 let mut err_msg = format!(
-                    "OAuth state mismatch: expected {}, got {}",
-                    expected_state, got
+                    "OAuth state mismatch (expected length={}, got length={})",
+                    expected_state.len(),
+                    got.len()
                 );
 
                 // Add helpful hint if truncation detected
@@ -307,7 +308,7 @@ pub fn parse_code_from_redirect(input: &str, expected_state: Option<&str>) -> Re
                     crate::auth::oauth_common::detect_url_truncation(input, expected_state.len())
                 {
                     let _ = write!(
-                        err_msg,
+                        &mut err_msg,
                         "\n\n💡 Tip: {}\n   \
                         Try copying ONLY the authorization code instead of the full URL.\n   \
                         The code looks like: eyJh...",

src/main.rs

@@ -1577,7 +1577,7 @@ fn set_owner_only_permissions(_path: &std::path::Path) -> Result<()> {
 fn is_pending_login_stale(pending: &PendingOAuthLogin) -> bool {
     if let Ok(created) = chrono::DateTime::parse_from_rfc3339(&pending.created_at) {
         let age = chrono::Utc::now().signed_duration_since(created);
-        age.num_hours() > 24
+        age > chrono::Duration::hours(24)
     } else {
         // If we can't parse the timestamp, consider it stale
         true