Release v4.22.1

Fixed

• The dark theme maps --color-error to the lighter red the field outline already uses and --color-error-bg to a deep red, so a field's validation message and Arc's command exception panel reach the WCAG AA 4.5:1 contrast on the dark surfaces instead of about 2.5:1. Every explicitly light root or subtree keeps the original red on a light background, including a light subtree under a root that is dark only because of the system setting. (#388)
• The README setup imports the stylesheets from a CSS entry file with @import, and documents the ambient declarations a TypeScript project needs to import them from TypeScript, so the documented setup type-checks on TypeScript 6 (TS2882). (#387)