v0.8.0

Stable Diffusion 3-Medium full MLX txt2img (#369)

From-scratch MLX port of SD3-Medium: MMDiT (24 joint transformer blocks) + AutoencoderKL VAE + FlowMatchEuler rectified-flow scheduler, in fusion_mlx/image/sd3/. Reuses mflux T5-XXL + CLIP-L, custom parametrized CLIP-G (20 heads). Wired into /v1/images/generate with model="sd3-medium" — supports negative_prompt and shift (unlike Flux). fp8 T5 (t5xxl_fp8_e4m3fn) preferred over sharded fp16 with auto-fallback. SD3_LOCAL_DIR for offline weight resolution. Real-model E2E validated. 28 unit tests.

See docs/sd3-image.md for usage, weights, and gotchas.