[Bug]: Model-level test connection fails with 'API key required' when only server-side key is configured

[cosarah]

Bug Description

In the Settings panel, when testing connectivity for a language model provider, the provider-level "Test Connection" button works correctly — it sends the request to the server, which can use server-side configured API keys (e.g. via environment variables). However, the model-level "Test Connection" button (inside the model edit dialog) has a client-side guard that immediately rejects the request if the client-side API key field is empty, even when the server has a valid API key configured.

Root cause: In components/settings/model-edit-dialog.tsx line 62, handleTestModel checks if (!editingModel || !apiKey) and short-circuits with an "API Key is required" error before ever sending the request to /api/verify-model. The provider-level test in components/settings/provider-config-panel.tsx does not have this guard and correctly delegates the check to the server.

Steps to Reproduce

1. Configure an API key for a provider only on the server side (e.g., set OPENAI_API_KEY in .env.local or server environment variables)
2. Do not enter an API key in the client-side Settings panel for that provider
3. Open Settings → select the provider → click "Test Connection" → ✅ Success
4. Click on a specific model under that provider to open the model edit dialog
5. Click "Test Connection" in the model edit dialog → ❌ Shows "API Key is required"

Expected Behavior

The model-level "Test Connection" should behave consistently with the provider-level test: send the request to the server and let the server-side API route handle API key resolution (falling back to server-configured keys when client-side key is empty).

Actual Behavior

The model-level test connection immediately shows "API Key is required" error without sending any request to the server, even though the server has a valid API key configured and the provider-level test works fine.

Deployment Method

Local development (pnpm dev)

Additional Context

The fix should remove or adjust the !apiKey guard in model-edit-dialog.tsx handleTestModel to match the provider-level behavior — letting the server handle API key validation.