#141166 Burndown: 数量 int64 溢出和检查访问器

#138309: parse boundary tests (18/19/20 digits, MinInt64/MaxInt64 +/- 1)
#140556, #140518, #140702: shared inf.Dec state (aliasing) fixes for #140744
#141170: baseline test matrix; each wrong-today field carries a TODO for its fixed value; suite green on master so it doubles as the burndown tracker
#138510: scaledValue negative rounding + tests
#140459: String() suffix drop for DecimalSI > 10^18
- #141817: regression from #140459. BinarySI values >= 1024 that are not a multiple of 1024 serialize in e notation when divisible by 10 (NewQuantity(5000000000, BinarySI) -> "5e9", was "5000000000"). Must land before 1.38.
#140674: MaxMilliQuantity + overflow docs
#138507: EBNF grammar fix for integer exponents
#141264: fix MinInt64 Neg/Sub via decimal fallback; extreme source scales tracked separately
#141169: switch validateBasicResource to Sign() < 0
#141181: stop using Value() …