Configure built-in retries across execution paths

internal/domain/domain.go

@@ -70,6 +70,7 @@ type RunRequest struct {
 	Execution        *ExecutionTargetOverride
 	Validation       *OutputContract
 	AppendedMessages []RenderedMessage
+	TransientRetries *int
 }
 
 // RunResult represents the complete result of a prompt execution run.

internal/domain/retries.go

@@ -0,0 +1,15 @@
+package domain
+
+import "fmt"
+
+// ResolveTransientRetries selects a nonnegative retry budget. A nil selection
+// inherits the supplied default.
+func ResolveTransientRetries(defaultBudget uint64, selection *int) (uint64, error) {
+	if selection == nil {
+		return defaultBudget, nil
+	}
+	if *selection < 0 {
+		return 0, fmt.Errorf("transient retries must not be negative")
+	}
+	return uint64(*selection), nil
+}