fix(theme): 浅色主题 ANSI 调色板重做到 WCAG AA + MCR/bold 动态开关 + antd 算法随亮度切换；github-light 底色柔化 #f6f8fa

tests/theme-contrast.mjs

@@ -0,0 +1,46 @@
+/**
+ * Builtin theme palette contrast gate. Light themes: foreground + all 16 ANSI
+ * colors must reach 4.5:1 against the theme background (WCAG AA body text);
+ * cursor must reach 3:1. Dark themes: only the foreground sanity check (>=4.5)
+ * — dark palettes are locked aesthetics, not regression targets here.
+ * Imports ../src/shared/theme.ts directly (zero-import module, Node >= 22.18).
+ * Run: node tests/theme-contrast.mjs  (must exit 0)
+ */
+import { BUILTIN_THEMES } from '../src/shared/theme.ts'
+
+let failed = 0
+const ok = (cond, msg) => {
+  console.log(`  ${cond ? 'ok' : 'FAIL'}: ${msg}`)
+  if (!cond) failed += 1
+}
+const L = (h) => {
+  const c = [1, 3, 5].map((i) => parseInt(h.slice(i, i + 2), 16) / 255)
+    .map((s) => (s <= 0.03928 ? s / 12.92 : ((s + 0.055) / 1.055) ** 2.4))
+  return 0.2126 * c[0] + 0.7152 * c[1] + 0.0722 * c[2]
+}
+const cr = (a, b) => {
+  const x = L(a), y = L(b)
+  return (Math.max(x, y) + 0.05) / (Math.min(x, y) + 0.05)
+}
+const ANSI = ['black', 'red', 'green', 'yellow', 'blue', 'magenta', 'cyan', 'white',
+  'brightBlack', 'brightRed', 'brightGreen', 'brightYellow', 'brightBlue',
+  'brightMagenta', 'brightCyan', 'brightWhite']
+const isLight = (bg) => L(bg) > 0.5
+
+for (const t of BUILTIN_THEMES) {
+  const c = t.colors
+  const light = isLight(c.background)
+  console.log(`${t.id} (${light ? 'light' : 'dark'}, bg ${c.background}):`)
+  ok(cr(c.foreground, c.background) >= 4.5, `foreground ${c.foreground} ${cr(c.foreground, c.background).toFixed(2)}`)
+  ok(cr(c.cursor, c.background) >= 3, `cursor ${c.cursor} ${cr(c.cursor, c.background).toFixed(2)}`)
+  if (!light) continue
+  for (const k of ANSI) {
+    ok(cr(c[k], c.background) >= 4.5, `${k} ${c[k]} ${cr(c[k], c.background).toFixed(2)}`)
+  }
+}
+
+if (failed > 0) {
+  console.error(`${failed} check(s) failed`)
+  process.exit(1)
+}
+console.log('theme-contrast: all ok')