feat: 完善 Compiler/PostCSS API

[sonofmagic]

Summary

• 完善 Compiler CSS finalization、Root API 与公开类型导出。
• 增加 source glob-aware invalidation、virtual CSS source 生命周期和 root 淘汰回调。
• 透传 template filename，并同步回归测试、API 文档和中文 changeset。

Verification

• pnpm install --frozen-lockfile
• pnpm build:ci
• pnpm --filter @weapp-tailwindcss/postcss test -- --coverage.enabled=false
• pnpm --filter weapp-tailwindcss exec vitest run test/compiler/core-compiler.test.ts test/compiler/core-compiler-lifecycle.test.ts --coverage.enabled=false
• pnpm --filter @weapp-tailwindcss/postcss lint
• pnpm --filter weapp-tailwindcss lint
• pnpm tsd:weapp-tailwindcss

全量 test:core 与 test:plugins 另有既有环境问题，详见任务记录。

Refs #1133
Refs #1134

[changeset-bot]

🦋 Changeset detected

Latest commit: 7d13743

The changes in this PR will be included in the next version bump.

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