### What happened?

For bare wildcard aliases using `model_name: "*"` (or the defensive `"*/"` variant), `/v1/models` currently applies wildcard expansion using the backing provider and can end up synthesizing provider-prefixed ids even when the alias itself has no provider namespace.

This is surprising for bare wildcard routes because the user-facing alias is intentionally provider-agnostic.

### Expected behavior

For bare wildcard routes only:

- `model_name: "*"` / `"*/"` should not add a synthetic provider prefix - `/v1/models` should preserve upstream model ids as returned by the provider discovery call - if upstream returns `model`, return `model` - if upstream returns `provider/model`, return `provider/model`

For explicit wildcard aliases like `deepseek/*`, `anthropic/*`, `openrouter/*`, existing behavior should remain unchanged.

### Why this matters

Bare wildcard aliases are used to present a provider-agnostic model list while still routing requests to multiple providers underneath. Auto-prepending a provider prefix changes the public alias contract and can make `/v1/models` noisier or less stable across providers.

### Repro config

```yaml model_list: - model_n…