dash: adapt feature_fastprune test for non-segwit

Since Dash doesn't have segwit/witness support, adapt the test to create
a large block using many regular transactions instead of using witness
data to inflate block size. This maintains the test's purpose of ensuring
-fastprune handles blocks larger than 64kb without crashing.

Author: Claude Code

test/functional/feature_fastprune.py

@@ -10,7 +10,6 @@
 from test_framework.blocktools import (
     create_block,
     create_coinbase,
-    add_witness_commitment
 )
 from test_framework.wallet import MiniWallet
 
@@ -23,16 +22,18 @@ def set_test_params(self):
     def run_test(self):
         self.log.info("ensure that large blocks don't crash or freeze in -fastprune")
         wallet = MiniWallet(self.nodes[0])
-        tx = wallet.create_self_transfer()['tx']
-        annex = [0x50]
-        for _ in range(0x10000):
-            annex.append(0xff)
-        tx.wit.vtxinwit[0].scriptWitness.stack.append(bytes(annex))
+
+        # Create many transactions to make a large block (>64kb)
+        # Since Dash doesn't have witness data, we need to create many regular transactions
+        txs = []
+        for _ in range(500):  # Create enough transactions to exceed 64kb
+            tx = wallet.create_self_transfer()['tx']
+            txs.append(tx)
+
         tip = int(self.nodes[0].getbestblockhash(), 16)
         time = self.nodes[0].getblock(self.nodes[0].getbestblockhash())['time'] + 1
         height = self.nodes[0].getblockcount() + 1
-        block = create_block(hashprev=tip, ntime=time, txlist=[tx], coinbase=create_coinbase(height=height))
-        add_witness_commitment(block)
+        block = create_block(hashprev=tip, ntime=time, txlist=txs, coinbase=create_coinbase(height=height))
         block.solve()
         self.nodes[0].submitblock(block.serialize().hex())
         assert_equal(int(self.nodes[0].getbestblockhash(), 16), block.sha256)