The interactive gate prompt guarded numeric choices with raw.isdigit(), but
str.isdigit() returns True for characters int() rejects — superscripts/subscripts
like '²'. So typing '²' passed the guard and int('²') raised an uncaught
ValueError, crashing the prompt loop. Use raw.isdecimal(), which is exactly the
decimal-digit set int() accepts (Numeric_Type=Decimal), so such input is treated
as an invalid choice and re-prompted. No behavior change for valid input.
Test: input '²' then '1' returns the first option (fails before: ValueError).
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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