fix(web): text on a tint of its own hue uses the house -fg tokens (#3150)

A hue painted as text on a color-mix tint of itself sits close to the
surface under it. On Minstrel's surfaces the raw accent on its 15% tint
measures 1.97:1 at worst (dark mode, hover surface), against AA's 4.5.

- tokens.json gains colors.fg: the five FabledSword -fg formulas (accent
  45%, success 45%, warning, error and info 50%), each mixed toward
  parchment so one declaration serves both modes. Success is Minstrel's
  moss. tokens-to-css emits them in :root.
- Tailwind exposes them as text-accent-fg, text-warning-fg, text-error-fg
  and text-info-fg.
- 23 sites swapped: 14 Tailwind class strings (PlayerBar and the admin
  count pills) and 9 CSS rules (StatusPill's four tones and five accent
  chips). Worst case after: accent-fg 5.03, error-fg 4.75, warning-fg
  4.92, success-fg 4.85.
- scripts/check-tint-contrast.js finds the pair in either spelling. Its
  test scans src in the web Vitest lane and fails on any new site, with
  fixture cases showing it can fail.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/scripts/tokens-to-css.test.js

@@ -5,7 +5,8 @@ const sample = {
   colors: {
     dark:  { obsidian: '#000', parchment: '#FFF' },
     light: { obsidian: '#FFF', parchment: '#000' },
-    flat:  { accent: '#4A6B5C', 'on-action': '#E8E4D8' }
+    flat:  { accent: '#4A6B5C', 'on-action': '#E8E4D8' },
+    fg:    { 'accent-fg': 'color-mix(in srgb, var(--fs-accent) 45%, var(--fs-parchment))' }
   },
   radii: { sm: '4px' },
   fontStacks: {
@@ -40,4 +41,13 @@ describe('tokens-to-css emit()', () => {
     expect(css).toContain('--fs-radius-sm: 4px;');
     expect(css).toContain("--fs-font-display: 'Fraunces', serif;");
   });
+
+  test('emits the -fg tokens in :root, not the light block', () => {
+    const css = emit(sample);
+    const root = css.match(/:root \{([\s\S]*?)\}/);
+    expect(root).not.toBeNull();
+    expect(root[1]).toContain('--fs-accent-fg: color-mix(in srgb, var(--fs-accent) 45%, var(--fs-parchment));');
+    const light = css.match(/\[data-theme="light"\] \{([\s\S]*?)\}/);
+    expect(light[1]).not.toContain('-fg');
+  });
 });