Flow Provider with Ollama: /api/generate returns empty AI Chat response, /api/chat fails Test Connection with 404

### Environment

* Flow Provider: Ollama
* Ollama Model: `gpt-oss:20b`

### Issue

I'm experiencing two different issues when configuring the Ollama Flow Provider.

#### Case 1: Using `/api/generate`

**Endpoint**

```text
http://[OLLAMA-SERVER]/api/generate
```

**Behavior**

* ✅ Test Connection succeeds.
* ❌ AI Chat returns an empty response (no output).

---

#### Case 2: Using `/api/chat`

**Endpoint**

```text
http://[OLLAMA-SERVER]/api/chat
```

**Behavior**

* ❌ Test Connection fails with:

```text
litellm.APIConnectionError: OllamaException - 404 page not found
```

---

### Verification

The same `/api/chat` endpoint works correctly when tested directly using Postman/cURL.

```bash
curl --location 'http://[OLLAMA-SERVER]/api/chat' \
--header 'Content-Type: application/json' \
--data '{
"model": "gpt-oss:20b",
"messages": [
{
"role": "system",
"content": "You are a helpful assistant."
},
{
"role": "user",
"content": "Hello!"
}
],
"stream": false
}'
```

**Response**

```json
{
"model": "gpt-oss:20b",
"created_at": "2026-07-22T08:17:24.694493298Z",
"message": {
"role": "assistant",
"content": "Hello! 👋 How can I help you today?",
"thinking": "The user says \"Hello!\". We should respond with a friendly greeting."
},
"done": true,
"done_reason": "stop",
"total_duration": 837122888,
"load_duration": 282868911,
"prompt_eval_count": 83,
"prompt_eval_duration": 40953169,
"eval_count": 59,
"eval_duration": 450009439
}
```

### Expected Behavior

* When using `http://[OLLAMA-SERVER]/api/chat`, the Test Connection should succeed.
* AI Chat should return the assistant response correctly.
* If `/api/generate` is supported, AI Chat should also produce the generated response instead of returning an empty message.

### Actual Behavior

| Endpoint | Test Connection | AI Chat |
| --------------- | -------------------------------------------------------------------- | ---------------- |
| `/api/generate` | ✅ Success | ❌ Empty response |
| `/api/chat` | ❌ `litellm.APIConnectionError: OllamaException - 404 page not found` | Cannot test |

### Additional Notes

* The Ollama server is reachable.
* The model is loaded and responds correctly.
* Direct requests to the Ollama API using Postman/cURL work as expected.
* The issue appears to be related to how the Flow Provider (or LiteLLM integration) is constructing or validating requests for Ollama endpoints, rather than an issue with the Ollama server itself.

Start by tracing the Flow Provider's Ollama integration and its LiteLLM request handling for /api/generate and /api/chat. Reproduce both cases with the supplied model and curl request, then verify that Test Connection succeeds for /api/chat and that AI Chat returns the assistant content for both supported endpoints.

Written by the indexing model from the issue text.