The first MT state-publication fix made the C count current before job
construction, but the Rust result still unconditionally copied its local
pre-job fill count back into `mtctx` after the callback returned. Preparing a
job clears `mtctx->inBuff.buffer` and `mtctx->inBuff.filled`, so the next stream
pass then observed a consumed range as if it were still active and returned a
generic error in the multi-file CLI test.
Keep the C-cleared state whenever job preparation has detached the active
range. Rust's filled count is published only while the C range remains active,
which covers the blocked/table-full path where no job reset occurred. The
callback still receives the current count before preparation, and the C90
projection declaration is kept before executable statements.
Test Plan:
- `cc -fsyntax-only -Werror=incompatible-pointer-types -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/compress/zstdmt_compress.c` -- passed
- `git diff --check` and `git diff --cached --check` -- passed
- The capped upstream suite reproduced a generic error in the multi-file CLI
path before this correction; the full rerun is pending
ddidderr
a57e0f83e1