Migrate model family to models manager (#7565)

This PR moves `ModelsFamily` to `openai_models`. It also propagates
`ModelsManager` to session services and use it to drive model family. We
also make `derive_default_model_family` private because it's a step
towards what we want: one place that gives model configuration.

This is a second step at having one source of truth for models
information and config: `ModelsManager`.

Next steps would be to remove `ModelsFamily` from config. That's massive
because it's being used in 41 occasions mostly pre launching `codex`.
Also, we need to make `find_family_for_model` private. It's also big
because it's being used in 21 occasions ~ all tests.

codex-rs/core/src/codex_delegate.rs

@@ -25,6 +25,7 @@ use crate::codex::Session;
 use crate::codex::TurnContext;
 use crate::config::Config;
 use crate::error::CodexErr;
+use crate::openai_models::models_manager::ModelsManager;
 use codex_protocol::protocol::InitialHistory;
 
 /// Start an interactive sub-Codex conversation and return IO channels.
@@ -35,6 +36,7 @@ use codex_protocol::protocol::InitialHistory;
 pub(crate) async fn run_codex_conversation_interactive(
     config: Config,
     auth_manager: Arc<AuthManager>,
+    models_manager: Arc<ModelsManager>,
     parent_session: Arc<Session>,
     parent_ctx: Arc<TurnContext>,
     cancel_token: CancellationToken,
@@ -46,6 +48,7 @@ pub(crate) async fn run_codex_conversation_interactive(
     let CodexSpawnOk { codex, .. } = Codex::spawn(
         config,
         auth_manager,
+        models_manager,
         initial_history.unwrap_or(InitialHistory::New),
         SessionSource::SubAgent(SubAgentSource::Review),
     )
@@ -88,9 +91,11 @@ pub(crate) async fn run_codex_conversation_interactive(
 /// Convenience wrapper for one-time use with an initial prompt.
 ///
 /// Internally calls the interactive variant, then immediately submits the provided input.
+#[allow(clippy::too_many_arguments)]
 pub(crate) async fn run_codex_conversation_one_shot(
     config: Config,
     auth_manager: Arc<AuthManager>,
+    models_manager: Arc<ModelsManager>,
     input: Vec<UserInput>,
     parent_session: Arc<Session>,
     parent_ctx: Arc<TurnContext>,
@@ -103,6 +108,7 @@ pub(crate) async fn run_codex_conversation_one_shot(
     let io = run_codex_conversation_interactive(
         config,
         auth_manager,
+        models_manager,
         parent_session,
         parent_ctx,
         child_cancel.clone(),