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.
REAPER's GetUserFileName serves both pickers — the no-save-picker finding was a
regex miss. A new enum value is structural, not additive: BankModel rejects an
out-of-range SourceMode/Tier rather than degrading.