Enhance documentation for Merchant Fee Deductible interface

- Added clarification in the gift documentation regarding tax and fee deductions when using the MerchantFeeDeductible interface.
- Updated the merchant fee deductible guide to specify that the fee is deducted from the recipient's deposit when transferring directly to a product implementing the interface.

Author: rez1dent3

docs/guide/purchases/gift.md

@@ -115,7 +115,8 @@ $item->balance; // 0
 
 The first user buys the product and gives it.
 
-> If the product uses the `Taxable` interface, then Santa will pay tax
+> If the product uses the `Taxable` interface, then Santa will pay tax.  
+> If the product uses the `MerchantFeeDeductible` interface, the fee is deducted from the merchant's payout instead.
 
 ```php
 $first->gift($last, $item);

docs/guide/purchases/merchant-fee-deductible.md

@@ -222,7 +222,7 @@ $item->balance; // 0
 
 ## Direct Transfers
 
-When transferring directly to a wallet that implements `MerchantFeeDeductible`, the fee is deducted from the recipient's deposit.
+When transferring directly to a product that implements `MerchantFeeDeductible`, the fee is deducted from the recipient's deposit.
 
 ```php
 $user = User::first();