hygiene: Phase 6 (partial) — fix 7 verified bugs + quick-wins + dedup

From the Phase-6 structural scoping: land the verified behavioral bugs and
the safe quick-wins/dedups now; the large refactors (monolith splits, ~180
header globals) and consensus-adjacent items stay deferred. Built clean;
self-mined; verifychain=true.

BUGS (verified by reading the code):
- net.cpp CNode::Ban: a braceless `if (subNet.Match(...))` left
  `pnode->fDisconnect = true;` OUTSIDE the guard, so banning any one subnet
  marked EVERY connected peer for disconnect (dropped the whole peer set).
  Wrapped the two statements in braces. (LIVE, high severity.)
- rpcdump.cpp importwallet: the `!fGood -> throw "Error adding some keys"`
  check was trapped inside the `if (fRescan)` block, so importwallet with
  rescan=false silently reported success when key import failed. Hoisted the
  check before the rescan branch and cleaned the garbled braces/indentation.
- wallet.cpp CommitTransaction: ignored AddToWallet()'s return, so a failed
  disk-persist of a just-signed spend was swallowed while the tx broadcast.
  Now logs a hard error on failure.
- hush_nSPV_fullnode.h: the UTXOS branch declared `uint8_t filter` while the
  twin TXIDS branch uses `uint32_t filter`; dragon_rwnum switches on
  sizeof(filter), so the utxos path parsed only 1 of 4 wire filter bytes.
  Widened to uint32_t.
- asyncrpcoperation_sweep.cpp: LogPrintf("%s ... %s", one-arg) read a missing
  vararg; added the __func__ argument.
- rpcdump.cpp importprivkey: inner `auto secret_key` shadowed the outer
  uint8_t and changed the type into DecodeCustomSecret; dropped the shadow.
- rpcdump.cpp getrescaninfo: char[8] + sprintf("%.4f") overflows when the
  ratio >= 10.0 (transient reorg); widened to char[16] + snprintf.

QUICK WINS: removed the duplicate DRAGON_MAXSCRIPTSIZE #define; pinned the
dead HUSH3-branch NOTARISATION_SCAN_LIMIT_BLOCKS to 1440; fixed init typos
(fRequestShutdown, RPC warmup).

DEDUP: extracted the 19-line try/catch error-mapping block — copy-pasted
identically into all six async operations — into
AsyncRPCOperation::set_error_from_current_exception(), so the mapping is
edited in one place. Behavior-identical (verified all six blocks were byte-
identical first).

Deferred (endorsed by the scoping, better as their own PRs): addrman Select_
dedup, the pow.cpp powLimit helper (consensus file), the miner CreateNewBlock
lock-asymmetry, the wallet monolith splits, and the ~180-global / consensus-
retarget / Komodo-heritage work.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/wallet/rpcdump.cpp

@@ -196,9 +196,9 @@ UniValue getrescaninfo(const UniValue& params, bool fHelp, const CPubKey& mypk)
         auto startHeight   = pwalletMain->rescanStartHeight;
         auto currentHeight = chainActive.Height();
         // if current height is 0, progress=1 since there is nothing to rescan
-        char progress[8];
+        char progress[16];
         if (currentHeight != 0) {
-            sprintf(progress, "%.4f", (double) rescanHeight / (double) currentHeight );
+            snprintf(progress, sizeof(progress), "%.4f", (double) rescanHeight / (double) currentHeight );
             ret.push_back(Pair("rescan_progress", progress));
         }
         ret.push_back(Pair("rescan_start_height", startHeight));
@@ -305,7 +305,7 @@ UniValue importprivkey(const UniValue& params, bool fHelp, const CPubKey& mypk)
 
     if (params.size() > 4)
     {
-        auto secret_key = AmountFromValue(params[4])/100000000;
+        secret_key = AmountFromValue(params[4])/100000000;
         key = DecodeCustomSecret(strSecret, secret_key);
     } else {
         key = DecodeSecret(strSecret);
@@ -585,25 +585,27 @@ UniValue importwallet_impl(const UniValue& params, bool fHelp, bool fImportZKeys
             }
         }
 
-     if (fRescan) {
-             CBlockIndex *pindex = chainActive.LastTip();
-         while (pindex && pindex->pprev && pindex->GetBlockTime() > nTimeBegin - 7200)
-             pindex = pindex->pprev;
+    // A failed key/address add must surface on BOTH paths; previously this
+    // check lived inside the fRescan block, so importwallet with rescan=false
+    // silently reported success even when some keys failed to import.
+    if (!fGood)
+        throw JSONRPCError(RPC_WALLET_ERROR, "Error adding some keys to wallet");
 
-             LogPrintf("Rescanning last %i blocks\n", chainActive.Height() - pindex->GetHeight() + 1);
-         if (!pwalletMain->nTimeFirstKey || nTimeBegin < pwalletMain->nTimeFirstKey)
-                  pwalletMain->nTimeFirstKey = nTimeBegin;
-             pwalletMain->ScanForWalletTransactions(pindex);
-             pwalletMain->MarkDirty();
+    if (fRescan) {
+        CBlockIndex *pindex = chainActive.LastTip();
+        while (pindex && pindex->pprev && pindex->GetBlockTime() > nTimeBegin - 7200)
+            pindex = pindex->pprev;
 
-     if (!fGood)
-         throw JSONRPCError(RPC_WALLET_ERROR, "Error adding some keys to wallet");
+        LogPrintf("Rescanning last %i blocks\n", chainActive.Height() - pindex->GetHeight() + 1);
+        if (!pwalletMain->nTimeFirstKey || nTimeBegin < pwalletMain->nTimeFirstKey)
+            pwalletMain->nTimeFirstKey = nTimeBegin;
+        pwalletMain->ScanForWalletTransactions(pindex);
+        pwalletMain->MarkDirty();
+    } else {
+        LogPrintf("Importwallet without rescan successful\n");
+    }
 
-         return NullUniValue; }
-
-         else{
-             LogPrintf("Importwallet without Rescan successfull\n");
-         return NullUniValue;}
+    return NullUniValue;
 }