* model_prefetch: add friendly API to pause comfy compiler
* sparse_attention: Pause comfy compiler for un-freed pieces
The VSA plan and pool stats do not free within the transformer causing
a comfy-compiler rogue allocation and graph break.
Ideally these should be freed in the lifetime of the transformer run
(and comfy-compiler scope) but there isnt a convenient place for the
particular lifecylce intended by these variables. So go with the pause()
approach.