fix(fullnode): reliable rescan completion + self-explaining shielded send errors

Two related fixes for the post-bootstrap "send fails / rescan stuck at 99%" trap:

1) Rescan completion now keys off warmup-end. A -rescan runs entirely inside daemon
   warmup (every RPC returns -28 until it finishes), so warmup completing IS the rescan
   completing. The old detectors relied on getrescaninfo (which some daemons answer with
   "Method not found") or a "Done rescanning"/bench log line the daemon may never print,
   leaving the status bar stuck at 99% — so users killed the rescan before it finished.
   When warmup ends and a rescan was confirmed active, clear the rescan state, flip to
   100%, refresh history/balance, and toast completion.

2) z_sendmany failures that mean stale shielded note data (shielded-requirements-not-met,
   missing sapling anchor, invalid sapling spend proof, bad-txns-sapling-*) now append a
   plain-language hint telling the user to run a full rescan, instead of surfacing only the
   raw daemon string.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app.cpp

@@ -431,6 +431,21 @@ wallet::LiteRolloutDecision resolveLiteRolloutDecision(config::Settings& setting
     }
     return decision;
 }
+
+// True when a z_sendmany failure means the wallet's shielded note data (witnesses/anchors) is
+// out of sync with the chain — the symptom after a bootstrap/reindex without a full rescan. These
+// are consensus/proof-build rejections, not user mistakes, and the only fix is a full rescan.
+bool sendErrorNeedsRescan(const std::string& raw)
+{
+    auto has = [&](const char* s) { return raw.find(s) != std::string::npos; };
+    return has("shielded-requirements-not-met") ||
+           has("shielded requirements not met") ||
+           has("missing sapling anchor") ||
+           has("Invalid sapling spend proof") ||
+           has("Invalid output proof") ||
+           has("bad-txns-sapling-") ||
+           has("anchor");
+}
 } // namespace
 
 void App::rebuildLiteWallet(bool force)
@@ -849,7 +864,10 @@ void App::update()
                 // Failures: route to the originating send UI when there is one (it shows
                 // its own error toast); otherwise surface a generic notification (this is
                 // how shield/merge/auto-shield failures become visible).
-                for (const auto& [opid, msg] : parsed.failureByOpid) {
+                for (const auto& [opid, rawMsg] : parsed.failureByOpid) {
+                    std::string msg = sendErrorNeedsRescan(rawMsg)
+                                          ? rawMsg + "\n\n" + TR("send_err_needs_rescan")
+                                          : rawMsg;
                     if (!invokeSendResultCallback(opid, false, msg)) {
                         ui::Notifications::instance().error(msg);
                     }

src/app_network.cpp

@@ -1144,6 +1144,26 @@ void App::refreshCoreData()
                     state_.warmup_description.clear();
                     connection_status_ = TR("connected");
                     VERBOSE_LOGF("[warmup] Daemon ready, warmup complete\n");
+
+                    // A -rescan runs entirely INSIDE daemon warmup (every RPC returns -28 until the
+                    // scan finishes), so warmup completing IS the rescan completing. This is the
+                    // reliable completion signal: some daemons lack getrescaninfo (it returns
+                    // "Method not found") or never print a "Done rescanning"/bench line, which left
+                    // the older detectors stuck at 99% — the user would then kill it prematurely.
+                    // rescan_confirmed_active_ ensures we actually observed this rescan running (set
+                    // by the getrescaninfo / daemon-log pollers) before declaring it done.
+                    if (state_.sync.rescanning && rescan_confirmed_active_) {
+                        state_.sync.rescanning = false;
+                        rescan_confirmed_active_ = false;
+                        state_.sync.rescan_progress = 1.0f;
+                        state_.sync.rescan_status.clear();
+                        // Notes/witnesses were rebuilt — force a fresh history + balance pull.
+                        transactions_dirty_ = true;
+                        last_tx_block_height_ = -1;
+                        invalidateShieldedHistoryScanProgress(true);
+                        ui::Notifications::instance().success("Blockchain rescan complete");
+                    }
+
                     NetworkRefreshService::applyConnectionInfoResult(state_, result.info);
                     // Trigger full data refresh now that daemon is ready
                     refreshData();

src/util/i18n.cpp

@@ -1293,6 +1293,7 @@ void I18n::loadBuiltinEnglish()
         strings_["send_tx_sent"] = "Transaction sent!";
         strings_["send_tx_success"] = "Transaction sent successfully!";
         strings_["send_status_unconfirmed"] = "Transaction status could not be confirmed";
+        strings_["send_err_needs_rescan"] = "Your wallet's shielded note data is out of date with the blockchain (this happens after a bootstrap or reindex). Run a full rescan via Settings -> Rescan Blockchain and let it finish completely, then try sending again.";
         strings_["send_txid_copied"] = "TxID copied to clipboard";
         strings_["send_txid_label"] = "TxID: %s";
         strings_["send_valid_shielded"] = "Valid shielded address";