floor the options column at the Options header width

[rootvector2]

appendOptions sizes the options column only from the rendered option entries and never from the header row, so once every option is narrower than the Options header the gap it computes for the header line, max - maxSince - HEADER_OPTIONS.length() + leftPad, is negative and createPadding runs new char[-3]. With setShowSince(true) that makes printHelp throw NegativeArraySizeException for something as ordinary as an app whose flags are -h and -v. Found while fuzzing the help output across option widths and pad settings.

determineMaxSinceLength already floors the since column at the width of the Since header; the option column just needs the same floor, so max now starts there when showSince is set. Keeping the bound next to the arithmetic that uses it leaves every createPadding argument in the method non-negative, and output is unchanged for any Options whose column was already that wide.

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