Add Chat Completions routing for Codex providers

- Add a Codex API format selector and routing badge for Chat Completions providers.
- Convert Codex Responses requests to upstream Chat Completions when routing is required.
- Convert Chat Completions JSON and SSE responses back to Responses format.
- Keep generated Codex wire_api values on Responses for Codex compatibility.
- Add i18n labels, provider metadata handling, and focused conversion tests.

src-tauri/src/proxy/providers/mod.rs

@@ -23,9 +23,11 @@ pub(crate) mod gemini_schema;
 pub mod gemini_shadow;
 pub mod models;
 pub mod streaming;
+pub mod streaming_codex_chat;
 pub mod streaming_gemini;
 pub mod streaming_responses;
 pub mod transform;
+pub mod transform_codex_chat;
 pub mod transform_gemini;
 pub mod transform_responses;
 
@@ -40,6 +42,7 @@ pub use claude::{
     claude_api_format_needs_transform, get_claude_api_format,
     transform_claude_request_for_api_format, ClaudeAdapter,
 };
+pub use codex::should_convert_codex_responses_to_chat;
 pub use codex::CodexAdapter;
 pub use gemini::GeminiAdapter;