Allow injecting the models manager into ThreadManager (#32911)

## Why

Embedding callers need to control whether model catalogs are persisted to disk.

## What changed

- Accept a shared models manager when constructing `ThreadManager` instead of always creating a cached manager internally.
- Add provider APIs for creating uncached model managers. OpenAI-compatible providers fetch on each `OnlineIfUncached` refresh without reading or writing `models_cache.json`.
- Keep existing app server, MCP server, sample, and test callers on the standard cached manager.

## Testing

- Verify an uncached manager fetches on every refresh.
- Verify an injected uncached manager controls thread refresh behavior and does not create `models_cache.json`.

GitOrigin-RevId: 8bb646054ecec4ccb865b2bf56249384916ea9db

codex-rs/models-manager/src/cache.rs

@@ -30,8 +30,8 @@ impl ModelsCacheManager {
     /// Attempt to load a fresh cache entry. Returns `None` if the cache doesn't exist or is stale.
     pub(crate) async fn load_fresh(&self, expected_version: &str) -> Option<ModelsCache> {
         info!(
-                cache_path = %self.cache_path.display(),
-                expected_version,
+            cache_path = %self.cache_path.display(),
+            expected_version,
             "models cache: attempting load_fresh"
         );
         let cache = match self.load().await {