v2.0.0: error-channel APIs, correctness fixes, and server hardening

BREAKING CHANGES:
- Guard interface: Guard(ctx Ctx) error; returning error short-circuits
  (subsequent guards and the method no longer execute)
- Wired[T]() (*T, error); New() may return error; failed wiring is sticky
- BindService/BindGuard/BindRoute return error; routes accept guards
  (guards receive merged query/form params as Ctx.State)
- registration panics after Start; Ctx.Ip honors X-Forwarded-For/X-Real-IP
- internal errors sanitized to fixed client messages

FIXES:
- int64 precision loss: /cell data decoded from raw JSON bytes and
  responses serialized with json.Number (no float64 round-trip)
- enum values range-checked before uint8 conversion (256 no longer
  truncates to 0 and slips through)
- logger: files failing name parsing are no longer deleted; log channel
  never blocks request goroutines; ConfigLogger is race-free;
  logWriterWorker unlock bug fixed
- stream writer panics recovered (process no longer crashes);
  streamDone closed exactly once
- generated Go client emits definitions for pointer-to-enum/struct fields
- anonymous structs rejected at registration; isPrivate safe on empty names
- removed dead Result.Id and RequestInfo.Type

ADDITIONS:
- graceful shutdown (Shutdown), StartOn, server timeouts by default
  (Read 60s/Idle 120s/Write off), SetTimeouts/SetMaxConcurrency
- big-int-safe JSON in the generated TS client (>2^53 as BigInt)
- example/ demo services and cmd/genexample artifact generator

example/demo/demo.go

@@ -0,0 +1,105 @@
+// Package demo 演示 fun 框架各特性的示例服务集：
+// 定宽整型与可空指针字段、枚举、业务错误码、NDJSON 流式（纯流 + 首条消息流）。
+// 产物参考见 example/gen（由 cmd/genexample 生成）。
+package demo
+
+import (
+	"github.com/cyi-cc/fun"
+)
+
+// OrderStatus 订单状态枚举：uint8 底层 + Names/DisplayNames
+type OrderStatus uint8
+
+func (OrderStatus) Names() []string        { return []string{"Pending", "Paid", "Shipped"} }
+func (OrderStatus) DisplayNames() []string { return []string{"待支付", "已支付", "已发货"} }
+
+// CreateOrderDto 下单参数。规则：非指针字段必传；指针/slice 字段可省略；
+// 数值一律定宽整型（int64），小数用 string 传输
+type CreateOrderDto struct {
+	Sku    string    // 必传
+	Count  int64     // 必传
+	Note   *string   // 可空
+	Status *OrderStatus // 可空，缺省 Pending
+	Tags   []string // 可省略
+}
+
+// OrderDto 订单视图。Id 为雪花 ID：全链路 int64 精度，TS 侧解析为 BigInt
+type OrderDto struct {
+	Id      int64
+	Status  OrderStatus
+	Amount  string   // 小数金额用字符串传输
+	Items   []string
+}
+
+type GetOrderDto struct {
+	Id int64
+}
+
+type CancelDto struct {
+	Id     int64
+	Reason *string
+}
+
+// OrderSvc 订单服务：普通请求/响应、无 DTO、error-only、业务错误码
+type OrderSvc struct {
+	fun.Ctx
+}
+
+func (s *OrderSvc) Create(dto CreateOrderDto) (OrderDto, error) {
+	return OrderDto{
+		Id:     9007199254740993, // 超过 2^53 的大整数示例
+		Status: OrderStatus(0),
+		Amount: "199.00",
+		Items:  dto.Tags,
+	}, nil
+}
+
+func (s *OrderSvc) Get(dto GetOrderDto) (OrderDto, error) {
+	return OrderDto{Id: dto.Id, Status: OrderStatus(1), Amount: "0.01"}, nil
+}
+
+// Cancel error-only 签名：无返回数据
+func (s *OrderSvc) Cancel(dto CancelDto) error {
+	if dto.Reason == nil {
+		// 业务错误：Code/Msg 原样透传给前端（status=2）
+		return fun.Error(4004, "必须填写取消原因")
+	}
+	return nil
+}
+
+type ChatDto struct {
+	Prompt string
+}
+
+type AskDto struct {
+	Prompt string
+}
+
+// ChatSvc 流式服务：纯流 + 首条消息流两种签名
+type ChatSvc struct {
+	fun.Ctx
+}
+
+// Chat 纯流式：响应为 application/x-ndjson，逐行推送
+func (s *ChatSvc) Chat(dto ChatDto) (*fun.Stream, error) {
+	st := &fun.Stream{}
+	go func() {
+		for _, chunk := range []string{"你好", "，这是", "流式示例"} {
+			if err := st.Send(chunk); err != nil {
+				return // 连接断开
+			}
+		}
+		st.Close() // 必须关闭，否则客户端一直等
+	}()
+	return st, nil
+}
+
+// Ask (T, stream, error)：T 作为流的第一条消息下发
+func (s *ChatSvc) Ask(dto AskDto) (string, *fun.Stream, error) {
+	st := &fun.Stream{}
+	go func() {
+		_ = st.Send("思考中...")
+		st.Close()
+	}()
+	return "收到：" + dto.Prompt, st, nil
+}