fix(cash): race between give transactor dispose and start on quick bg/fg

services/opencode/src/main/kotlin/com/getcode/opencode/internal/transactors/GiveBillTransactor.kt

@@ -112,6 +112,10 @@ internal class GiveBillTransactor(
      * @return the confirmed [TransactionMetadata.SendPublicPayment] on success.
      */
     suspend fun start(): Result<TransactionMetadata.SendPublicPayment> {
+        if (!scope.isActive) {
+            return logAndFail(GiveTransactorError.Other(message = "Transactor was disposed"))
+        }
+
         val ownerKey = owner
             ?: return logAndFail(GiveTransactorError.Other(message = "No owner key. Did you call with() first?"))
         val desiredToken = token
@@ -212,13 +216,13 @@ internal class GiveBillTransactor(
 
     /** Cancels the coroutine scope and clears all held state. */
     fun dispose() {
+        scope.cancel()
         owner = null
         presentationData = BillPresentationData(emptyList(), emptyList())
         rendezvousKey = null
         receivingAccount = null
         token = null
         providedVerifiedState = null
-        scope.cancel()
     }
 
     sealed class GiveTransactorError(

services/opencode/src/main/kotlin/com/getcode/opencode/managers/BillTransactionManager.kt

@@ -26,6 +26,7 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancel
+import kotlinx.coroutines.ensureActive
 import kotlinx.coroutines.launch
 import java.util.Timer
 import java.util.TimerTask
@@ -113,6 +114,10 @@ class BillTransactionManager @Inject constructor(
             present(transactor.presentationData)
             presentBillForGive(onTimeout)
 
+            // If cancelAwaitForGrab() fired between present() and here,
+            // bail out before start() reads fields that dispose() may have nulled.
+            ensureActive()
+
             transactor.start()
                 .onSuccess {
                     childScope.cancel()