Codex plugin login status misreporting for Azure model provider

Hi there! Thanks for the great plugin — really looking forward to using Codex from Claude Code.

## Description

I have Codex CLI configured with an Azure OpenAI model provider via `config.toml`, and everything works great with `codex -p`. However, I noticed that `codex login status` returns exit code 1 with "Not logged in" in this setup, which seems to only check for OAuth-based login.

**My config.toml:**
```toml
model = "gpt-5.4"
model_provider = "azure"

[model_providers.azure]
name = "Azure OpenAI"
base_url = ".openai.azure.com/openai/v1&quot
env_key = "AZURE_OPENAI_API_KEY"
wire_api = "responses"
```

```
$ codex login status
Not logged in # exit code 1

$ codex -p "hello"
# works perfectly fine
```

## Impact

The companion plugin uses `getCodexLoginStatus()` as a gate before running reviews or tasks. Since this check doesn't recognize Azure provider authentication, Azure users see:

> Codex CLI is not authenticated. Run `!codex login` and retry.

This prevents us from using `/codex:review` and `/codex:task` in Claude Code, even though the underlying Codex CLI works perfectly.

## Suggestion

Would it be possible for `codex login status` (or `getCodexLoginStatus()` in the plugin) to also consider non-OAuth authentication methods? For example, when a custom `model_provider` with an `env_key` is configured, the check could verify that the corresponding environment variable is set.

## Environment

- Codex CLI: 0.117.0
- codex-plugin-cc: 1.0.0
- OS: macOS...