[MCP] Dedicated error message for GitHub MCPs missing a personal access token (#5393)

Because the GitHub MCP is one of the most popular MCPs and it
confusingly doesn't support OAuth, we should make it more clear how to
make it work so people don't think Codex is broken.

codex-rs/core/src/mcp/auth.rs

@@ -10,10 +10,16 @@ use tracing::warn;
 use crate::config_types::McpServerConfig;
 use crate::config_types::McpServerTransportConfig;
 
+#[derive(Debug, Clone)]
+pub struct McpAuthStatusEntry {
+    pub config: McpServerConfig,
+    pub auth_status: McpAuthStatus,
+}
+
 pub async fn compute_auth_statuses<'a, I>(
     servers: I,
     store_mode: OAuthCredentialsStoreMode,
-) -> HashMap<String, McpAuthStatus>
+) -> HashMap<String, McpAuthStatusEntry>
 where
     I: IntoIterator<Item = (&'a String, &'a McpServerConfig)>,
 {
@@ -21,14 +27,18 @@ where
         let name = name.clone();
         let config = config.clone();
         async move {
-            let status = match compute_auth_status(&name, &config, store_mode).await {
+            let auth_status = match compute_auth_status(&name, &config, store_mode).await {
                 Ok(status) => status,
                 Err(error) => {
                     warn!("failed to determine auth status for MCP server `{name}`: {error:?}");
                     McpAuthStatus::Unsupported
                 }
             };
-            (name, status)
+            let entry = McpAuthStatusEntry {
+                config,
+                auth_status,
+            };
+            (name, entry)
         }
     });