feat: harden trading SDK examples

examples/trading_client/README.md

@@ -0,0 +1,13 @@
+# Trading Client Construction
+
+[中文](README_CN.md)
+
+Shows two client-construction patterns: `TradingClient::new` for one wallet and `TradingClient::from_infrastructure` for wallets sharing RPC and SWQoS clients.
+
+This is a configuration template. Set `PRIVATE_KEY`, RPC, and every enabled provider credential; it initializes network clients but does not submit a trade.
+
+```bash
+cargo run --package trading_client
+```
+
+Initialize the client before subscribing to events. Do not construct it in a trading callback.

examples/trading_client/README_CN.md

@@ -0,0 +1,13 @@
+# TradingClient 创建方式
+
+[English](README.md)
+
+展示两种客户端创建模式：单钱包使用 `TradingClient::new`，多钱包通过 `TradingClient::from_infrastructure` 共享 RPC 和 SWQoS 客户端。
+
+这是配置模板。运行前设置 `PRIVATE_KEY`、RPC 和所有已启用服务商凭证；程序会初始化网络客户端，但不会提交交易。
+
+```bash
+cargo run --package trading_client
+```
+
+客户端应在事件订阅前完成初始化，不要在交易回调中创建。

examples/trading_client/src/main.rs

@@ -13,7 +13,6 @@ use sol_trade_sdk::{
     AstralaneTransport, TradingClient, TradingInfrastructure,
 };
 use solana_commitment_config::CommitmentConfig;
-use solana_sdk::signature::Keypair;
 use std::sync::Arc;
 
 #[tokio::main]
@@ -35,7 +34,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 ///
 /// Use this when you have a single wallet or don't need to share infrastructure.
 async fn create_trading_client_simple() -> AnyResult<TradingClient> {
-    let payer = Keypair::from_base58_string("use_your_payer_keypair_here");
+    let payer = sol_trade_sdk::common::keypair::load_keypair_from_env("PRIVATE_KEY")?;
     let rpc_url = "https://mainnet.helius-rpc.com/?api-key=xxxxxx".to_string();
     let commitment = CommitmentConfig::processed();
 
@@ -73,7 +72,7 @@ async fn create_trading_client_simple() -> AnyResult<TradingClient> {
 /// Use this when you have multiple wallets sharing the same configuration.
 /// The infrastructure (RPC client, SWQOS clients) is created once and shared.
 async fn create_trading_client_from_infrastructure() -> AnyResult<TradingClient> {
-    let payer = Keypair::from_base58_string("use_your_payer_keypair_here");
+    let payer = sol_trade_sdk::common::keypair::load_keypair_from_env("PRIVATE_KEY")?;
     let rpc_url = "https://mainnet.helius-rpc.com/?api-key=xxxxxx".to_string();
     let commitment = CommitmentConfig::processed();