Fix wrong trie root: don't bypass validation for force-scheduled tasks

The force-schedule fallback (stall prevention) was setting
skipCheck[nextTx] = true, which tells the validator to accept the
result without checking state consistency. This is only correct for
the task at maxValidated+1 (the validation frontier), where all
predecessors are guaranteed validated. For a non-frontier task, this
can accept results computed against stale state, producing wrong
trie roots.

Remove the skipCheck flag from the force-schedule path. The task is
still dispatched and executed; its result goes through normal
validation and gets re-executed if invalid.

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

Author: 2 people

execution/stagedsync/exec3_parallel.go

@@ -1904,7 +1904,10 @@ func (be *blockExecutor) scheduleExecution(ctx context.Context, pe *parallelExec
 		nextTx := be.execTasks.takeNextPending()
 		if nextTx >= 0 {
 			execTask := be.tasks[nextTx]
-			be.skipCheck[nextTx] = true
+			// Do NOT set skipCheck here — the task is not at the validation
+			// frontier (maxValidated+1), so its result must go through normal
+			// validation. Setting skipCheck would accept stale-state results
+			// and produce wrong trie roots.
 			be.cntExec++
 
 			version := execTask.Version()