Muse Code with any OpenAI-compatible gateway

# Muse Code — Custom Provider & No Meta Login

Use **Muse Code** (`muse`) with any OpenAI-compatible API without creating a Meta account or using `muse login`.

Muse Code's `meta` provider defaults to `https://api.meta.ai/v1`, but you can point it at your own gateway. The `meta` label is just a provider name — storing a key with `muse auth set --provider meta` does **not** require a Meta OAuth login. `muse login` is optional and only for Meta's hosted auth; API-key auth is enough.

> **⚠️ Muse Code 1.0.1 changed things.** The old per-invocation `--base-url` flag no longer sends your auth header (the bearer is "withheld" unless the base URL is pinned in settings). If you're on **1.0.1+**, use the [`endpoint_transport` settings method](#3-pin-your-gateway-in-settings-101) below. The old `--base-url` wrapper only works on **0.2.x** — see [the legacy section](#legacy-02x-wrapper---base-url).

## Why

- Route Muse Spark (`muse-spark-1.2`, etc.) through a gateway/proxy (e.g., self-hosted, OpenCode, Helicone, Cloudflare AI Gateway, LiteLLM)
- Avoid `muse login` / browser OAuth entirely
- Keep the same CLI (`muse exec`, `muse` TUI) while swapping the backend

## Quick start (no Meta account)

### 1. Install Muse Code

```bash
curl -fsSL https://dev.meta.ai/install.sh | sh
muse --version  # Muse Code 1.0.1 (or newer)
```

### 2. Store an API key (no browser)

> This does NOT create a Meta account. It just saves a key under the `meta` provider name.

```bash
# paste your gateway/proxy API key on stdin (never as an argv)
echo -n "YOUR_GATEWAY_API_KEY" | muse auth set --provider meta --api-key-stdin

# verify
cat ~/.config/muse/auth.json  # { "schema_version": 1, "providers": { "meta": { "api_key": "..." } } }

# alternative: env var (takes priority over file)
export META_API_KEY="YOUR_GATEWAY_API_KEY"
```

You never need to run `muse login`.

### 3. Pin your gateway in settings (1.0.1+)

Muse Code 1.0.1 hardens endpoint overrides: a bare `--base-url` flag is treated as "off the sanctioned front door" and **your Authorization header will not be sent** to it. The sanctioned opt-in is a settings pin — edit `~/.config/muse/settings.json`:

```json
{
  "schema_version": 1,
  "model": "muse-spark-1.2",
  "provider": "meta",
  "endpoint_transport": {
    "base_url": "http://127.0.0.1:8914/v1",
    "auth": "bearer"
  }
}
```

- `base_url` — your gateway / proxy root (same valu