feat: add input-number component

[isaquebock]

Summary

• New webkit component inputs/input-number: spec-driven monolithic numeric input with sizes (small/medium/large), min/max/step, optional spinner column, prefix/suffix slots, and a lock indicator in the disabled state.
• Visual states match the input-text v2 pattern: hover gated by :not(:focus-within), focus-within ring with offset, --danger-border/--warning-border for invalid/required.
• Native <input type=\"number\"> under the hood — modelValue is always numeric; clearing the input falls back to min ?? 0.
• Storybook: Default / Sizes / Disabled / Invalid, all fully reactive (v-model bound), with hand-written code snippets for the Show code panel (same convention as feat/inputs-select).
• Adds Event and HTMLInputElement to the shared ESLint globals so components using native DOM types lint clean.

Test plan

• pnpm webkit:lint passes
• pnpm --filter storybook build succeeds
• Open Storybook → Webkit › Inputs › InputNumber and exercise:
  • Default story — type and click chevrons; v-model updates; min/max/step clamp
  • Sizes story — three sizes side-by-side, each with its own v-model
  • Disabled story — typing and chevrons blocked; lock icon visible
  • Invalid story — danger border applied; interaction still works
• Keyboard: Tab focuses, ↑/↓ increment/decrement, Enter commits and fires change
• Native browser spinner is hidden; only the custom chevron column renders
• Visual diff against the Figma frame (InputNumber at node 3714:10789) across hover/focus/filled/invalid/required/disabled × 3 sizes