Add buy_exact_sol_in and buy_exact_quote_in instruction support

- Add BUY_EXACT_SOL_IN_DISCRIMINATOR for PumpFun
- Add BUY_EXACT_QUOTE_IN_DISCRIMINATOR for PumpSwap
- Add use_exact_in_instruction field to SwapParams
- When enabled, uses exact input instructions that spend exactly the
  specified SOL/quote amount with slippage applied to output tokens
- Defaults to false for backwards compatibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib.rs

@@ -508,6 +508,7 @@ impl TradingClient {
             fixed_output_amount: params.fixed_output_token_amount,
             gas_fee_strategy: params.gas_fee_strategy,
             simulate: params.simulate,
+            use_exact_in_instruction: false,
         };
 
         // Validate protocol params
@@ -617,6 +618,7 @@ impl TradingClient {
             fixed_output_amount: params.fixed_output_token_amount,
             gas_fee_strategy: params.gas_fee_strategy,
             simulate: params.simulate,
+            use_exact_in_instruction: false,
         };
 
         // Validate protocol params