SX's (str 1e-7) gives "1e-07" but JS spec is "1e-7" — no padding, no
leading zeros in the exponent (sign stays). We stepped through:
mant "e" expraw → mant "e" (sign (strip-zeros body))
Added four small helpers: js-normalize-num-str, js-split-sign,
js-strip-leading-zeros, js-strip-zeros-loop. All pure string walkers.
Unit 521/522, slice 148/148 unchanged.
String 40 → 42, Number 75 → 76 (+3 total).
Fixes S9.8.1_A9_T1, fromCharCode/S9.7_A3.1_T1..T2 family.
giles
b2810db1a0