Fall back to HTTP immediately for oversized WebSocket requests (#60840)

## Why

A WebSocket close with code `1009` before any text arrives indicates that the request exceeds the peer's message size limit. Retrying the request over another WebSocket does not address that limit.

## What changed

- Classify these early size rejections as requiring HTTP fallback and switch transports without exhausting WebSocket retries, including during prewarming.
- Preserve ordinary stream retry behavior for size closes after any text frame and for other close codes.

## Testing

Add integration coverage for early size rejections during generation and prewarming, size closes after metadata, rate limits, or response creation, and ordinary closes.

GitOrigin-RevId: 4550d289bb414fec1faae2a195bcc635d394117b

codex-rs/cli/src/doctor.rs

@@ -2512,6 +2512,7 @@ fn websocket_error_detail(err: &ApiError) -> String {
         }
         // These variants format fixed text; retry metadata is typed and never printed.
         ApiError::ContentFilter
+        | ApiError::WebsocketMessageTooLarge
         | ApiError::ContextWindowExceeded
         | ApiError::QuotaExceeded
         | ApiError::UsageNotIncluded