auth: move domain mode below app wire types (#29721)

## Why

Authentication mode is a domain concept used by login, model selection,
telemetry, and transports. Keeping the canonical type in app-server
protocol forces those lower-level crates to depend on an unrelated wire
API.

## What changed

- Added canonical `codex_protocol::auth::AuthMode` domain values.
- Kept the app-server wire DTO unchanged and added an explicit app-side
conversion.
- Removed production app-server-protocol dependencies from login,
model-provider-info, models-manager, and otel call paths.

## Stack

This is PR 2 of 6, stacked on [PR
#29714](https://github.com/openai/codex/pull/29714). Review only the
delta from `codex/split-json-rpc-protocols`. Next: [PR
#29722](https://github.com/openai/codex/pull/29722).

## Validation

- Auth and login coverage passed in the focused protocol/domain test
run.
- App-server account and auth conversion coverage passed.

codex-rs/core-plugins/src/loader.rs

@@ -15,7 +15,6 @@ use crate::remote::RemoteInstalledPlugin;
 use crate::store::PluginStore;
 use crate::store::plugin_version_for_source;
 use crate::store::plugin_version_for_source_with_fallback_manifest;
-use codex_app_server_protocol::AuthMode;
 use codex_config::ConfigLayerStack;
 use codex_config::HooksFile;
 use codex_config::types::McpServerConfig;
@@ -39,6 +38,7 @@ use codex_plugin::PluginHookSource;
 use codex_plugin::PluginId;
 use codex_plugin::PluginIdError;
 use codex_plugin::app_connector_ids_from_declarations;
+use codex_protocol::auth::AuthMode;
 use codex_protocol::protocol::Product;
 use codex_protocol::protocol::SkillScope;
 use codex_utils_absolute_path::AbsolutePathBuf;