Clamps insertSuffix's underflow, floors uniqueEntryName's validity guard, suppresses
the redundant overwrite confirm via a picker out-param, adds a PayloadBuffer
high-water mark, and corrects stale CLAUDE.md/CMake claims.
Pure planner classifies missing/unreadable/unrepresentable and repairs transport
names; the verb digests, streams and commits atomically over a const session.
Both pickers now ride GetUserFileName (mode 0/1); the "no save picker" premise was false.
Landing uses O_EXCL so the create is the existence check, not a TOCTOU pair.