Refresh OpenRouter models after setting API key (#58551)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

## Summary

Adding an OpenRouter API key did not populate the model list until the
app was
restarted. `set_api_key` stored the credential but never triggered a
model
fetch, so until re-authentication happened (on restart or a settings
change)
the picker showed only the user-configured `settings.available_models`,
not the
models returned by the OpenRouter API.

This makes `set_api_key` refresh the models right after the key is
stored,
mirroring how `authenticate` already does it.

## Changes

- `set_api_key` awaits the credential store and then calls
`restart_fetch_models_task`, so the API model list loads immediately
after a
  key is entered (and is cleared when the key is removed).
- `fetch_models` now maps `list_models` errors via
`LanguageModelCompletionError::from`, preserving the real OpenRouter
error
  message instead of wrapping it in a generic `Other(...)`.

Release Notes:

- Fixed OpenRouter models not appearing until restart after adding an
API key

Signed-off-by: Zhiwei Liang <zhiwei.liang@zliang.me>

crates/language_models/src/provider/open_router.rs

@@ -59,13 +59,20 @@ impl State {
     fn set_api_key(&mut self, api_key: Option<String>, cx: &mut Context<Self>) -> Task<Result<()>> {
         let credentials_provider = self.credentials_provider.clone();
         let api_url = OpenRouterLanguageModelProvider::api_url(cx);
-        self.api_key_state.store(
+        let task = self.api_key_state.store(
             api_url,
             api_key,
             |this| &mut this.api_key_state,
             credentials_provider,
             cx,
-        )
+        );
+
+        cx.spawn(async move |this, cx| {
+            let result = task.await?;
+            this.update(cx, |this, cx| this.restart_fetch_models_task(cx))
+                .ok();
+            Ok(result)
+        })
     }
 
     fn authenticate(&mut self, cx: &mut Context<Self>) -> Task<Result<(), AuthenticateError>> {
@@ -103,12 +110,7 @@ impl State {
         cx.spawn(async move |this, cx| {
             let models = list_models(http_client.as_ref(), &api_url, &api_key, &extra_headers)
                 .await
-                .map_err(|e| {
-                    LanguageModelCompletionError::Other(anyhow::anyhow!(
-                        "OpenRouter error: {:?}",
-                        e
-                    ))
-                })?;
+                .map_err(LanguageModelCompletionError::from)?;
 
             this.update(cx, |this, cx| {
                 this.available_models = models;
@@ -125,7 +127,7 @@ impl State {
             let task = self.fetch_models(cx);
             self.fetch_models_task.replace(task);
         } else {
-            self.available_models = Vec::new();
+            self.available_models.clear();
         }
     }
 }