test: report what a running redrive has left to move

The TypeScript suite covers this and the Ruby suite did not.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: cardmagic

test/integration/redrive_test.rb

@@ -174,6 +174,17 @@ def touch
     assert_equal 0, SolidObjects.redrives.find(task.id, authorization_context: "operator").moved
   end
 
+  test "reports what a running task has left to move" do
+    dead_effects(25)
+
+    task = SolidObjects.dead_letters.effects.redrive(limit: 15, authorization_context: "operator")
+    assert_equal 15, task.remaining
+
+    SolidObjects::RedriveRunner.new.run_once
+
+    assert_equal 5, SolidObjects.redrives.find(task.id, authorization_context: "operator").remaining
+  end
+
   test "reads tasks back by id and by status" do
     dead_effects(5)
     task = SolidObjects.dead_letters.effects.redrive(authorization_context: "operator")