fix: keep numeric filter arguments as long through bounds checks - #842

Fixes #841.

split, abbreviate and slice read numeric arguments as Long but narrowed them with intValue() before the bounds checks, so values beyond the int range wrapped:

• split clamps the limit to the int range, so a huge limit still means "all the parts"
• abbreviate compares length as long, so a huge width returns the input unchanged and a wrapped negative is no longer possible
• slice keeps fromIndex/toIndex as long through the checks and now also validates fromIndex against the input size when toIndex is omitted (previously a raw StringIndexOutOfBoundsException escaped)

Regression tests cover one failing case per filter; SplitFilterTest and CoreFiltersTest pass 103/103.

I audited every intValue() call in the codebase for the same pattern. These three filters were the only real bugs: