.NET: [Feature]: docs example for PZERO OpenAI-compatible endpoint

@rogerbarreto is already working on this.

Since Aug 31, 2026.

### Description

Microsoft Agent Framework already talks to OpenAI-compatible hosts via the OpenAI chat client (custom endpoint / `base_url`). People looking for prepaid, privacy-first inference still have to guess the host, key format, and catalog id.

A named PZERO example would let users paste and run. No first-party PZERO package required. Search for `pzero` returned none.

Expected behavior: docs (Python and/or .NET) include this snippet under custom OpenAI-compatible endpoints. Users who find this issue can convert today even if the docs PR is not merged.

### Code Sample

Python. Use `OpenAIChatCompletionClient` (chat completions) unless you have verified the Responses path for your call shape. `OpenAIChatClient` is the Responses client.

```python
import os
from agent_framework.openai import OpenAIChatCompletionClient

client = OpenAIChatCompletionClient(
model_id="deepseek-v4-flash",
api_key=os.environ["PZERO_API_KEY"],
base_url="https://api.pzero.studio/v1",
)
```

`base_url` is the `/v1` root, not `/v1/chat/completions`. Pass the catalog id as-is. Docs page: https://learn.microsoft.com/en-us/agent-framework/integrations/openai-endpoints

Get a key: https://pzero.studio/agents (sign-in free; min top-up 1 USDC on Base; no starter credits). Live text ids: `GET https://api.pzero.studio/v1/models` (public, no key).

Smoke:

```bash
curl -sS -X POST "https://api.pzero.studio/v1/chat/completions" \
-H "Authorization: Bearer $PZERO_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"Hello from PZERO"}],"stream":false}'
```

I am not asking for a bundled `PzeroChatClient`. Do not start implementation on my behalf until the board says Ready; the snippet is for users today.

Every AI Credit is at least 20% off $1 list. Usage is paid.

### Language/SDK

Both