Suppress UI transaction notifications during initial block download

During IBD, every wallet transaction triggers NotifyTransactionChanged
which repaints the Qt transaction list. With thousands of staking
rewards across 2M blocks, this floods the event loop and makes the
wallet appear frozen ("not responding") for hours.

Skip NotifyTransactionChanged during IsInitialBlockDownload(). The UI
catches up naturally via refreshWallet() once sync completes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/wallet.cpp

@@ -486,7 +486,8 @@ void CWallet::WalletUpdateSpent(const CTransaction &tx, bool fBlock)
                     printf("WalletUpdateSpent found spent coin %s TRI %s\n", FormatMoney(wtx.GetCredit()).c_str(), wtx.GetHash().ToString().c_str());
                     wtx.MarkSpent(txin.prevout.n);
                     wtx.WriteToDisk();
-                    NotifyTransactionChanged(this, txin.prevout.hash, CT_UPDATED);
+                    if (!IsInitialBlockDownload())
+                        NotifyTransactionChanged(this, txin.prevout.hash, CT_UPDATED);
                 }
             }
         }
@@ -503,7 +504,8 @@ void CWallet::WalletUpdateSpent(const CTransaction &tx, bool fBlock)
                 {
                     wtx.MarkUnspent(&txout - &tx.vout[0]);
                     wtx.WriteToDisk();
-                    NotifyTransactionChanged(this, hash, CT_UPDATED);
+                    if (!IsInitialBlockDownload())
+                        NotifyTransactionChanged(this, hash, CT_UPDATED);
                 }
             }
         }
@@ -634,8 +636,9 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn)
         // since AddToWallet is called directly for self-originating transactions, check for consumption of own coins
         WalletUpdateSpent(wtx, (wtxIn.hashBlock != 0));
 
-        // Notify UI of new or updated transaction
-        NotifyTransactionChanged(this, hash, fInsertedNew ? CT_NEW : CT_UPDATED);
+        // Notify UI of new or updated transaction (skip during IBD to avoid flooding the event loop)
+        if (!IsInitialBlockDownload())
+            NotifyTransactionChanged(this, hash, fInsertedNew ? CT_NEW : CT_UPDATED);
 
         // notify an external script when a wallet transaction comes in or is updated
         std::string strCmd = GetArg("-walletnotify", "");
@@ -2775,7 +2778,7 @@ void CWallet::UpdatedTransaction(const uint256 &hashTx)
         LOCK(cs_wallet);
         // Only notify UI if this transaction is in this wallet
         map<uint256, CWalletTx>::const_iterator mi = mapWallet.find(hashTx);
-        if (mi != mapWallet.end())
+        if (mi != mapWallet.end() && !IsInitialBlockDownload())
             NotifyTransactionChanged(this, hashTx, CT_UPDATED);
     }
 }