feat: v3.2 类型安全 state + 全局响应信封 + 便利 schema

[yourtion]

Summary

由 one-api phase2-server dogfooding 驱动的三块 ergonomics 改进：

• typed state：ERest<T, Raw, State> 实例级泛型，ctx.state 类型安全（消除鉴权值 as 断言）。State 须用 type alias 定义。
• 全局 response envelope：setResponseEnvelopers({success, error, testUnwrapper}) 注册后，registerTyped handler 进入 return 模式（return data → 框架自动包装信封），告别手写 ok()/fail() + 每处 reply.json(ok(x))。
• 便利 schema + 测试返回类型：z.anyObject() 别名（等价 z.object({}).catchall(z.unknown())）；success<T>() 返回类型从 response schema 推导。

附带：registerTyped handler 第二参数从 reply 统一为 ctx（Context<State, Raw>，含 ctx.reply + ctx.state），保留 raw 逃生舱强类型。

Breaking（仅当启用新特性时）

• registerTyped handler 签名 (req, reply) => void → (req, ctx) => data
• ctx.state 类型由 State 泛型驱动（默认 Record<string, unknown> 向后兼容）

详见 MIGRATION.md。

Test Plan

• erest：287 测试全绿（含新增 test-any-object / test-state-types / test-envelope）
• erest：typecheck exit 0 + oxlint 0 errors + oxfmt 格式正确
• one-api phase2-server 适配验证：31 e2e 全绿，typecheck 无错（净减 29 行）
• 向后兼容：未注册 enveloper / 未声明 State / 未声明 response schema 时维持 v3.1 行为

[codecov]

Codecov Report

❌ Patch coverage is 91.01124% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.47%. Comparing base (1c1cc2e) to head (d4bff4b).

Files with missing lines	Patch %	Lines
src/lib/params.ts	58.33%	5 Missing ⚠️
src/lib/index.ts	90.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #192      +/-   ##
==========================================
+ Coverage   91.64%   92.47%   +0.82%     
==========================================
  Files          28       28              
  Lines        2837     2882      +45     
  Branches      722      748      +26     
==========================================
+ Hits         2600     2665      +65     
+ Misses        235      215      -20     
  Partials        2        2              

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