Keep the converter->pruner checkpoint/no-checkpoint case (the issue's
headline: an older completed ask must not survive while the newest
oversized typed ask is dropped) and one boundary case covering multipart
clipping, the token-estimator budget for CJK text, and an oversized
mixed text+image boundary that now retains no older ask (behaviour change:
previously the oversized boundary was skipped and an older ask kept).
Also drop the provenance-footer disclaimer from the docstring.
Parallel fix in #131819 by liuhao1024 credited here.
Co-authored-by: liuhao1024 <sunsky.lau@gmail.com>
fe422a690a