* ggml-webgpu: makes the flash attn vec path compile and size its split/reduce work from the device’s reported subgroup range instead of assuming 32 subgroup size.
* ggml-webgpu: remove the extra max_wg_size >= max_subgroup_size guard. Remove hardcoded 32 when determine the value of reduce_wg_size and vec_nwg_cap
* ggml-webgpu: add tile flash attention fallback
* ggml-webgpu: add new fields and discard usage of mnk for tile version
* ggml-webgpu: modify the vec path to discard the mnk parameter
* ggml-webgpu: enable flash attention vec and tile version for broswer
* ggml-webgpu: stagging KV for flash attention tile version
* formatting
* turn on subgroup uniformity check
* remove Q_TILE as it is always 1 for vec path
* make row_max and exp_sum to local register
* make different bindings with same underlying buffer to have the same usage flags
* move path selection into the shader library and have the host consume a single flash-attn decision object.
* turn off skip_validation and address buffer overlapping when nwg==1
* formatting
* merge binding when kv overlap
