Enable MCP OAuth refresh coordination by default (#55701)

## What changed

Mark `mcp_oauth_refresh_coordination` as stable and enable it by default.

GitOrigin-RevId: f82074c7d148808ceeb4acd206bbadefd470e5b1

codex-rs/features/src/lib.rs

@@ -1609,8 +1609,8 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::McpOAuthRefreshCoordination,
         key: "mcp_oauth_refresh_coordination",
-        stage: Stage::UnderDevelopment,
-        default_enabled: false,
+        stage: Stage::Stable,
+        default_enabled: true,
     },
     FeatureSpec {
         id: Feature::UseXaa,