[RFC] ffpa-attn 0.3.0 roadmap

[DefTruth]

• (512, 1024] headdim support for Hopper (via CuTeDSL backend)
• KV Cache (FWD/BWD) support
• SM120 FP8 Attention (FWD), headdim [64, 1024] @DefTruth
• SM120 FP4 Attention (FWD), headdim [64, 1024] @DefTruth
• CuTeDSL backend autouner @Butterfingrz
• SM100 Blackwell head_dim=512 specialization (via CuTeDSL backend) @Butterfingrz