Add a locale-aware renderer-independent number input

[woksin]

Consumer need

A representative custom-token design-system consumer still requires a locale-aware InputNumber supplied by PrimeReact. Components 4's command NumberField uses native type="number", which does not preserve locale grouping/decimal parsing, fraction-digit policy, prefix/suffix composition, and the same min/max UX.

This is a real bounded Prime island rather than a reason to put Prime back into Components.

Direction

Design a Cratis-owned, renderer-independent locale-aware number input only after confirming the representative consumer contract:

• number | null public boundary;
• BCP 47 locale from CratisComponentsProvider;
• grouping and decimal separators;
• minimum/maximum fraction digits;
• min/max/step;
• optional prefix/suffix;
• accessible spinbutton semantics and validation;
• command-field adapter through Arc's existing asCommandFormField seam;
• stable parts/tokens and native fallback behavior.

Do not expose React Aria or another formatter's types publicly.

Acceptance

• The representative consumer's NumberInput behavior compiles and passes interaction/locale specs without Prime.
• nb-NO, en-US, keyboard, screen-reader, invalid, disabled, and mobile behavior are covered.
• Documentation explains when to use native NumberField versus the locale-aware primitive.