Refresh existing form-field styling app-wide

A one-off visual refresh of the current form-field controls.

Applies to the existing FormField (text/number/date/dropdown wrappers), DropDown, and DatePicker:

• Lighter default border — border-stroke-5 instead of border-stroke-10.

• Ring-based focus (focus:ring-2 focus:ring-stroke-30/15) so focus no longer shifts layout by changing border width.

• Regular-weight placeholders (placeholder:font-regular).

• Fix the dead disabledx:text-label-disabled typo so disabled field text actually greys out for the first time.

Reference: spike st/form-and-control-updates restyles these files in place — take only the recolour here, not the spike's added variants (those land as net-new components in the field-kit stories).

Note: formField.tsx has since gained a description prop on main that rewrote its label rendering — re-apply the recolour on top of it, don't overwrite.