🤗 Kernels: Major Updates

The 🤗 Kernels project, which standardizes custom kernel packaging and distribution, has undergone major updates. Key changes include a new "kernel" repository type on the Hub for better discoverability and specific compute needs. Security has been significantly enhanced with trusted kernel publishers and code signing using Sigstore’s cosign. CLIs for kernels and kernel-builder are now leaner, and framework coverage has expanded to include Torch Stable ABI and Apache TVM FFI, laying groundwork for agentic kernel development.