feat(pay): paywatch selfcheck + money-critical 验证 runbook(#34/34A)

selfcheck 子命令:用 PAY_ACCOUNT_XPUB 打印前 N 个派生收款地址,供与自己钱包/Ian Coleman
逐个核对(派生错=钱打到无私钥地址)。README 加『收真钱前必过』四步验证:①金标准测试
②Ian Coleman 独立交叉核对 ③真钱包 A selfcheck 比对 ④真链 1 USDT 收→控→测→归闭环。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pay/README.md

@@ -25,6 +25,40 @@ xpub 派生,**不持私钥**),轮询 TronGrid 侦测到账、确认后标记订
    助记词、Coin=TRX 对照前 3 个地址。一致 = 派生实现可信;不一致 = 有 bug,别上线。
 5. 助记词 A/B 分开冷存 + Bitwarden。**只把 xpub_A 交给本服务。**
 
+## Money-critical 验证(收任何真钱之前必须全过)
+
+派生错 = 把买家的钱打到你没私钥的地址,钱直接丢。上真钱前逐步核死:
+
+**① 代码自检(金标准向量)**
+```bash
+cd pay && go test ./internal/wallet -run TestKnownVector -v   # 必须 PASS
+```
+
+**② 独立交叉核对(证明代码 vs 独立实现一致)** —— 断网开 Ian Coleman `bip39-standalone.html`,
+输入测试助记词 `abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about`,
+Coin=TRX、BIP44,核对 Derived Addresses 前 3 行必须等于:
+```
+m/44'/195'/0'/0/0  TUEZSdKsoDHQMeZwihtdoBiN46zxhGWYdH
+m/44'/195'/0'/0/1  TSeJkUh4Qv67VNFwY8LaAxERygNdy6NQZK
+m/44'/195'/0'/0/2  TYJPRrdB5APNeRs4R7fYZSwW3TcrTKw2gx
+```
+且 Account Extended Public Key = `xpub6D1AabNHCupeiLM65ZR9UStMhJ1vCpyV4XbZdyhMZBiJXALQtmn9p42VTQckoHVn8WNqS7dqnJokZHAHcHGoaQgmv8D45oNUKx6DZMNZBCd`。
+
+**③ 你的真钱包 A(护你自己钱的那道闸,最重要)** —— 用你钱包 A 的真 account xpub:
+```bash
+PAY_ACCOUNT_XPUB="<你钱包A的account xpub>" go run ./cmd/paywatch selfcheck 5
+```
+把输出的地址,和你钱包 A(在 Ian Coleman 里同一 xpub、或 TronLink/imToken 里钱包 A)显示的
+地址 0..4 **逐个比对**。**全部一致才可上线收款;有一个不一致,立即停,别收任何钱。**
+
+**④ 真链闭环(Phase E,最终证明)** —— 小额:
+1. `POST /order` 拿地址 → 往它转 **1 USDT(TRC20)**。
+2. 用你钱包 A 打开 → **确认这 1 USDT 出现在你钱包 A 名下**(证明你确实控制这个地址)。
+3. `GET /order/{id}` 应变 `paid`(证明 watcher 侦测正确)。
+4. 用 `cmd/sweep` 把这 1 USDT 归集到冷钱包 B → **确认 B 收到**(证明签名/广播正确)。
+
+全过 = 收→控→测→归 四环闭合,可放量。
+
 ## 运行
 
 ```bash

pay/cmd/paywatch/main.go

@@ -16,6 +16,7 @@ package main
 
 import (
 	"context"
+	"fmt"
 	"log/slog"
 	"net/http"
 	"os"
@@ -28,6 +29,7 @@ import (
 	"github.com/wangjia/pangolin/pay/internal/pay"
 	"github.com/wangjia/pangolin/pay/internal/store"
 	"github.com/wangjia/pangolin/pay/internal/tron"
+	"github.com/wangjia/pangolin/pay/internal/wallet"
 	"github.com/wangjia/pangolin/pay/internal/watcher"
 )
 
@@ -38,7 +40,39 @@ func env(k, def string) string {
 	return def
 }
 
+// selfcheck prints the first N receiving addresses derived from PAY_ACCOUNT_XPUB.
+// MONEY-CRITICAL: compare these against your own wallet app / iancoleman.io for
+// the SAME account xpub. If they don't match, the service would hand buyers
+// addresses you cannot spend — do NOT accept any payment until they match.
+func selfcheck() {
+	xpub := os.Getenv("PAY_ACCOUNT_XPUB")
+	if xpub == "" {
+		fmt.Fprintln(os.Stderr, "PAY_ACCOUNT_XPUB is required")
+		os.Exit(1)
+	}
+	n := 5
+	if len(os.Args) > 2 {
+		if v, err := strconv.Atoi(os.Args[2]); err == nil && v > 0 {
+			n = v
+		}
+	}
+	fmt.Println("Derived receiving addresses (compare against your wallet for this xpub):")
+	for i := 0; i < n; i++ {
+		addr, err := wallet.AddressFromAccountXpub(xpub, 0, uint32(i))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "derive %d: %v\n", i, err)
+			os.Exit(1)
+		}
+		fmt.Printf("  m/44'/195'/0'/0/%d  ->  %s\n", i, addr)
+	}
+}
+
 func main() {
+	if len(os.Args) > 1 && os.Args[1] == "selfcheck" {
+		selfcheck()
+		return
+	}
+
 	log := slog.New(slog.NewJSONHandler(os.Stdout, nil))
 
 	xpub := os.Getenv("PAY_ACCOUNT_XPUB")