49: Add high-level Jupiter position decrease operation

src/main/tjava/com/r35157/libs/jupiter/perps/JupiterPerpsService.tjava

@@ -132,6 +132,31 @@ public interface JupiterPerpsService {
             @NotNull SolanaSignedTransaction transaction
     ) throws IOException, InterruptedException;
 
+    /**
+     * Decreases an existing Jupiter Perps position.
+     *
+     * <p>The service constructs the transaction, asks the supplied wallet to
+     * sign it, and submits it to Jupiter.</p>
+     *
+     * @param wallet the wallet that owns the position
+     * @param positionAccount the Jupiter Perps position to decrease
+     * @param receiveTokenMint the mint address of the token to receive
+     * @param sizeUsdDelta the requested decrease in position size, denominated in USD
+     * @param maxSlippageBps the maximum accepted slippage, in basis points
+     * @return the Solana transaction signature
+     * @throws IllegalArgumentException if an amount, mint, or slippage value is invalid
+     * @throws IOException if the transaction cannot be constructed, signed, or submitted
+     * @throws InterruptedException if the calling thread is interrupted
+     */
+    @NotNull
+    ΩSolanaTransactionSignatureΩ executePositionDecrease(
+            @NotNull SolanaWallet wallet,
+            @NotNull ΩJupiterPerpsPositionAccountΩ positionAccount,
+            @NotNull ΩSPLMintAddressΩ receiveTokenMint,
+            @NotNull ΩUSDCAmountΩ sizeUsdDelta,
+            int maxSlippageBps
+    ) throws IOException, InterruptedException;
+
     /**
      * Constructs an unsigned Solana transaction for decreasing
      * an existing Jupiter Perps position.

src/main/tjava/com/r35157/libs/jupiter/perps/impl/anchoridl/AnchorIdlJupiterPerpsServiceImpl.tjava

@@ -221,6 +221,28 @@ public class AnchorIdlJupiterPerpsServiceImpl implements JupiterPerpsService {
         return response.txid();
     }
 
+    @Override
+    public @NotNull ΩSolanaTransactionSignatureΩ executePositionDecrease(
+            @NotNull SolanaWallet wallet,
+            @NotNull ΩJupiterPerpsPositionAccountΩ positionAccount,
+            @NotNull ΩSPLMintAddressΩ receiveTokenMint,
+            @NotNull ΩUSDCAmountΩ sizeUsdDelta,
+            int maxSlippageBps
+    ) throws IOException, InterruptedException {
+        SolanaUnsignedTransaction unsignedTransaction =
+                buildPositionDecreaseTransaction(
+                        positionAccount,
+                        receiveTokenMint,
+                        sizeUsdDelta,
+                        maxSlippageBps
+                );
+
+        SolanaSignedTransaction signedTransaction =
+                wallet.signTransaction(unsignedTransaction);
+
+        return executePositionDecreaseTransaction(signedTransaction);
+    }
+
     @Override
     public @NotNull SolanaUnsignedTransaction buildPositionDecreaseTransaction(
             @NotNull ΩJupiterPerpsPositionAccountΩ positionAccount,