fix: enforce public contrast and audit rank errors

src/lib/theme-contrast.ts

@@ -1,5 +1,40 @@
 type Rgb = readonly [number, number, number];
 
+export type PublicThemeColors = Record<string, string>;
+export interface ContrastPair { name: string; foreground: string; background: string }
+
+export function derivePublicForegrounds(c: PublicThemeColors) {
+  const value = (key: string, fallback: string) => c[key] ?? fallback;
+  const background = value("color_background", "#f8fafc");
+  const surface = value("color_surface", "#ffffff");
+  const dropdown = value("color_dropdown", surface);
+  const navbar = value("color_navbar", surface);
+  const primary = value("color_primary", "#f59e0b");
+  const accent = value("color_accent", "#10b981");
+  const make = (name: string, preferred: string, bg: string): ContrastPair => ({
+    name, foreground: readableColor(preferred, [bg]), background: bg,
+  });
+  const pairs = [
+    make("body", value("color_text", "#0f172a"), background),
+    make("surface", value("color_text", "#0f172a"), surface),
+    make("muted", value("color_text_muted", "#64748b"), surface),
+    make("link", value("link_color", primary), surface),
+    make("link-hover", value("link_hover_color", primary), surface),
+    make("navbar", value("color_navbar_text", "#1e293b"), navbar),
+    make("dropdown", value("color_text", "#0f172a"), dropdown),
+    make("primary", value("button_text_color", "#1e293b"), primary),
+    make("accent", "#ffffff", accent),
+    make("button-primary", value("button_text_color", "#1e293b"), value("button_primary_color", primary)),
+    make("button-secondary", value("button_secondary_text_color", "#ffffff"), value("button_secondary_color", "#22c55e")),
+    make("button-danger", value("button_danger_text_color", "#ffffff"), value("button_danger_color", "#ef4444")),
+    make("button-outline", value("button_outline_text_color", "#1a1a2e"), surface),
+    make("pill", value("color_text", "#0f172a"), surface),
+    make("badge", value("button_text_color", "#1e293b"), primary),
+    make("overlay", "#ffffff", "#111827"),
+  ];
+  return { pairs, byName: Object.fromEntries(pairs.map((pair) => [pair.name, pair.foreground])) };
+}
+
 export function contrastRatio(foreground: string, background: string): number | null {
   const fg = parseHex(foreground);
   const bg = parseHex(background);