Make HK sidebar menu text always 100% visible

- Set muted sidebar text equal to the readable sidebar text so inactive
  nav items and section labels are never dimmed
- Active item remains distinguished by its accent background and border

src/lib/theme-css.ts

@@ -34,7 +34,7 @@ export function adminPaletteCss(admin: AdminPalette): string {
   const parts: string[] = [
     `--admin-sidebar-background:${admin.sidebar};`,
     `--admin-sidebar-text-readable:${admin.sidebarText};`,
-    `--admin-sidebar-muted-readable:color-mix(in srgb, var(--admin-sidebar-text-readable) 82%, transparent);`,
+    `--admin-sidebar-muted-readable:var(--admin-sidebar-text-readable);`,
     `--admin-input-text-readable:${readableColor(admin.text, [admin.canvas, admin.surface])};`,
     `--admin-canvas:${admin.canvas};`,
     `--admin-surface:${admin.surface};`,