feat: harden trading SDK examples

examples/shared_infrastructure/README.md

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+# Shared Infrastructure
+
+[中文](README_CN.md)
+
+Demonstrates sharing one `TradingInfrastructure` across multiple wallet-specific `TradingClient` values. This reduces connection, memory, and initialization overhead in multi-wallet services.
+
+Replace the RPC, SWQoS credentials, and all wallet placeholders in `src/main.rs`. The example initializes clients and prints sharing information; it does not submit a trade.
+
+```bash
+cargo run --package shared_infrastructure
+```
+
+Only share infrastructure when wallets use the same RPC, commitment, and submission routes. Keep wallet signing and position state isolated.

examples/shared_infrastructure/README_CN.md

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+# 多钱包共享基础设施
+
+[English](README.md)
+
+展示多个钱包专属 `TradingClient` 共享一份 `TradingInfrastructure`，降低多钱包服务的连接数、内存和初始化开销。
+
+运行前替换 `src/main.rs` 中的 RPC、SWQoS 凭证和全部钱包占位值。示例只初始化客户端并打印共享信息，不提交交易。
+
+```bash
+cargo run --package shared_infrastructure
+```
+
+只有钱包使用相同 RPC、commitment 和提交通道时才共享基础设施；签名权限和持仓状态仍必须按钱包隔离。