feat: harden trading SDK examples

examples/simple_trading/README.md

@@ -0,0 +1,16 @@
+# Simple Trading API
+
+[中文](README_CN.md)
+
+This is the recommended starting point for `SimpleBuyParams`, `SimpleSellParams`, `BuyAmount`, `SellAmount`, account policies, recent blockhashes, and durable nonces.
+
+The example constructs parameters but does not submit the commented buy/sell calls. Set `PRIVATE_KEY` and replace protocol-state placeholders before adapting it to a live integration.
+
+```bash
+export RPC_URL=https://your-rpc.example
+cargo run --package simple_trading
+```
+
+`WithMaxInput` protects maximum quote cost and is generally appropriate when fill priority matters. `ExactInput` protects minimum output and may fail more often in active markets. `HotPathMinimal` requires all needed token accounts to exist; normal integrations should use `AccountPolicy::Auto`.
+
+See [Trading Parameters](../../docs/TRADING_PARAMETERS.md) and [Low-Latency Bots](../../docs/LOW_LATENCY_BOTS.md).

examples/simple_trading/README_CN.md

@@ -0,0 +1,16 @@
+# 简化交易 API
+
+[English](README.md)
+
+这是学习 `SimpleBuyParams`、`SimpleSellParams`、`BuyAmount`、`SellAmount`、账户策略、recent blockhash 和 durable nonce 的推荐入口。
+
+示例只构造参数，买卖调用保持注释状态。用于真实集成前必须设置 `PRIVATE_KEY` 并替换协议状态占位值。
+
+```bash
+export RPC_URL=https://your-rpc.example
+cargo run --package simple_trading
+```
+
+`WithMaxInput` 保护最大 quote 成本，适合优先成交；`ExactInput` 保护最小输出，在活跃市场更容易失败。`HotPathMinimal` 要求所需 token 账户均已存在，普通接入应使用 `AccountPolicy::Auto`。
+
+参见[交易参数说明](../../docs/TRADING_PARAMETERS_CN.md)和[低延迟 Bot 指南](../../docs/LOW_LATENCY_BOTS_CN.md)。

examples/simple_trading/src/main.rs

@@ -18,11 +18,11 @@ use sol_trade_sdk::{
     SolanaTrade, TradeTokenType,
 };
 use solana_commitment_config::CommitmentConfig;
-use solana_sdk::{hash::Hash, pubkey::Pubkey, signature::Keypair, signer::Signer};
+use solana_sdk::{hash::Hash, pubkey::Pubkey, signer::Signer};
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    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 = std::env::var("RPC_URL")
         .unwrap_or_else(|_| "https://api.mainnet-beta.solana.com".to_string());
     let commitment = CommitmentConfig::processed();