wallet: fix consolidation-scheduler wedge (ran every block; dead mutual-exclusion)

The Sapling auto-consolidation scheduler never advanced nextConsolidation after
init and never set fConsolidationRunning, so once the tip passed the init
threshold `-consolidation` dispatched a consolidation op every block instead of
once per -consolidationinterval, and every guard that reads fConsolidationRunning
(in RunSaplingSweep, and in the new autoshield driver) was dead.

Mirror the intended scheduler model:
- RunSaplingConsolidation sets fConsolidationRunning=true before dispatch and
  self-guards with `if (fConsolidationRunning) return;`.
- The consolidation op advances nextConsolidation = consolidationInterval +
  tipHeight and clears fConsolidationRunning on every terminal state
  (success/failure/exception/cancel), guarded by op id so only the current op
  mutates scheduler state.
- saplingConsolidationOperationId moved to public so the op can read it.

Restores the documented once-per-interval cadence and makes the
sweep/consolidation/autoshield mutual-exclusion guards effective.

Note: the sweep op has the same latent wedge (fSweepRunning/nextSweep are
cleared only on the sweepComplete success path, so a cancelled or throwing
sweep leaves fSweepRunning stuck true) - left for a follow-up; this commit is
the template to port.

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

src/wallet/asyncrpcoperation_saplingconsolidation.cpp

@@ -28,8 +28,17 @@ AsyncRPCOperation_saplingconsolidation::AsyncRPCOperation_saplingconsolidation(i
 AsyncRPCOperation_saplingconsolidation::~AsyncRPCOperation_saplingconsolidation() {}
 
 void AsyncRPCOperation_saplingconsolidation::main() {
-    if (isCancelled())
+    if (isCancelled()) {
+        // Only the current op owns the scheduler flag; a stale/cancelled op must
+        // not clear it out from under a freshly-enqueued successor.
+        if (pwalletMain) {
+            LOCK(pwalletMain->cs_wallet);
+            if (getId() == pwalletMain->saplingConsolidationOperationId) {
+                pwalletMain->fConsolidationRunning = false;
+            }
+        }
         return;
+    }
 
     set_state(OperationStatus::EXECUTING);
     start_execution_clock();
@@ -76,6 +85,21 @@ void AsyncRPCOperation_saplingconsolidation::main() {
     LogPrintf("%s", s);
     unlock_notes(); // clean up
     LogPrint("zrpc", "%s: consolidation input notes unlocked\n", getId());
+
+    // Advance the interval and clear the running flag on EVERY terminal state
+    // (success, failure, exception) so consolidation runs once per interval
+    // instead of every block, and a failed round still lets the next one fire.
+    // Only the CURRENT op does this bookkeeping. This fixes the pre-existing
+    // wedge where nextConsolidation never advanced and fConsolidationRunning
+    // was never set/reset.
+    if (pwalletMain) {
+        LOCK2(cs_main, pwalletMain->cs_wallet);
+        if (getId() == pwalletMain->saplingConsolidationOperationId) {
+            int tipHeight = (chainActive.Tip() != NULL) ? chainActive.Tip()->GetHeight() : targetHeight_;
+            pwalletMain->nextConsolidation     = pwalletMain->consolidationInterval + tipHeight;
+            pwalletMain->fConsolidationRunning = false;
+        }
+    }
 }
 
 bool AsyncRPCOperation_saplingconsolidation::main_impl() {