mlx-native 0.15.8

What's Changed

• test(residency): observe retired mappings with a live device by @robertelee78 in #68
• test(gguf): measure existing small-row quantized routes by @robertelee78 in #65
• fix(observer): retain async owners and explicit rotation scopes by @robertelee78 in #69

Full Changelog: v0.15.7...v0.15.8