Integrate FormatterModifier into the validation message modifier chain,
enabling StringFormatter formatters to be used as pipe modifiers in
message templates (e.g., {{input|uppercase}}, {{input|mask:1-4:X}}).
This requires bumping respect/string-formatter to ^1.7.
Add feature tests for both the Formatted validator (uppercase, lowercase,
trim, number, date, creditCard, secureCreditCard, chained formatters) and
the FormatterModifier in templates (all major formatters, custom parameters,
multi-argument modifiers, and chained modifiers).
Assisted-by: Claude Code (Claude Opus 4.6)
