feat(unocss): use ant-* prefixed keys for font-size tokens to avoid colliding with built-in rem scale

[Copilot]

buildFontSizeTheme/buildTextTheme used bare keys (sm, lg, xl, h1…) that, when allowUnprefixed: true, generated text-sm/text-lg rules that silently overrode the UnoCSS/Tailwind built-in rem scale.

Changes

• common/theme.ts — Rename all font-size/text theme keys to ant-* (ant-sm, ant-base, ant-lg, ant-xl, ant-h1, ant-h2, ant-h3). The DEFAULT key is replaced by ant-base.
• common/autocomplete.ts — Update FONT_ENUM / TEXT_ENUM to reflect the new key names.
• preset.test.ts — Add assertions that bare keys (sm, lg, DEFAULT) are absent from the theme, ant-* keys resolve to the correct var(--ant-font-size-*) values, and the rule regex matches text-ant-sm / a-text-ant-sm.
• README.md — Document new text-ant-* utility names and explain the coexistence design.

Before / After

<!-- before: overrides UnoCSS built-in 0.875rem -->
<span class="text-sm">…</span>

<!-- after: built-in scale untouched; Ant token opt-in -->
<span class="text-sm">…</span>          <!-- → 0.875rem (UnoCSS built-in) ✅ -->
<span class="text-ant-sm">…</span>      <!-- → var(--ant-font-size-sm)     ✅ -->
<span class="a-text-ant-lg">…</span>    <!-- → var(--ant-font-size-lg)     ✅ -->

No changes to spacing, color, shadow, or border-radius tokens — only the font-size key namespace is affected.

[ayangweb]

@copilot 我刚才忘了问你，tailwindcss 需要改吗？会不会也有冲突？