docs: document version=2 (pinned) and revision=main (always-latest) load options; note no zero-arg default in kernels lib

v1.6: kernel-repo distribution fix

v1.5: exact chunked backward (kda_chunk_step_exact_bwd)

v1.4: forward optimizations (decode key-fold, batched decode, exact prefill, head-interleaved prefill)

README: document kernel-type repo + get_kernel load path

v1.3: fused multi-chunk backward

v1.2: training / backward support

v1.1: T-KDA-02 state-decay axis fix + fully model-agnostic

v1.0: KDA NKI kernels for HF Transformers on AWS Trainium