Enable git attribution across Codex entry points (#34819)

## What changed

- Install the git attribution extension in the app server, MCP server, and `codex debug prompt-input` so authenticated workspace policy controls the commit and pull request attribution instructions sent to the model.
- Resolve attribution settings from the process-level ChatGPT base URL, independent of per-thread or per-tool configuration overrides.
- Treat git attribution as contextual developer content when mapping model events.

## Testing

- Cover policy fetch retries, workspace switches, rollbacks, cold thread resumes with legacy instructions, MCP tool calls, and prompt-debug output.

GitOrigin-RevId: 57d182c432c20d7c1c6c429057b6163c9f32088d

codex-rs/app-server/src/message_processor.rs

@@ -274,6 +274,8 @@ impl MessageProcessor {
                         goal_service: Arc::clone(&goal_service),
                         environment_manager: Arc::clone(&environment_manager_for_extensions),
                         executor_skill_provider: Arc::clone(&executor_skill_provider),
+                        git_attribution_base_url: config.chatgpt_base_url.clone(),
+                        http_client_factory: config.http_client_factory(),
                         thread_store: Arc::clone(&thread_store),
                     },
                 ),