test: remember a re-sent key once

A parity audit found the same untested branch in both languages. A key
can finish twice on one actor: retention removes the message, the
enqueue path no longer deduplicates it, and the caller sends it again.
The list must move the key to the end rather than repeat it, and nothing
proved that. Without the move the new test reads
`["first", "second", "first"]`.

The changelog and the roadmap did not record that the doctor now catches
a half-applied migration.

Validation: bundle exec rake (785 runs, 0 failures).

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

Author: cardmagic

CHANGELOG.md

@@ -38,6 +38,12 @@
   `db/migrate`. Seven scripts each carried a hand-copied migration list, and
   three of them applied an incomplete schema. A test fails if any script names a
   migration class again.
+- Report a half-applied migration in `solid_objects doctor`. The column list
+  omitted `instances.state_revision`, `messages.operation`,
+  `effects.success_operation`, `effects.failure_operation`, and
+  `dead_letters.operation`, so an application that skipped a migration read as
+  healthy and found out from a worker crash. A test fails when the list does not
+  name a column that a migration after the first adds.
 
 - Retry a dead effect or broadcast. `SolidObjects.dead_letters` keeps its
   message meaning and answers `effects` and `broadcasts`, so the kind rides on

docs/roadmap.md

@@ -58,7 +58,9 @@
   cannot reject the subscription or stop its siblings
 - Reconciliation read APIs
 - Installation doctor, authorization reference, fit guide, and legacy-state
-  migration cookbook
+  migration cookbook. The doctor names every column that a migration after the
+  first adds, so a half-applied migration fails the schema check rather than
+  reaching a worker. A test holds the list to that rule
 - Database server verification: each adapter reports its version against a
   tested minimum, MySQL confirms Solid Objects tables use InnoDB, and the
   doctor warns rather than refusing to run on an untested server

test/integration/result_lookup_test.rb

@@ -294,6 +294,19 @@ def reject_checkout
     assert_raises(SolidObjects::MessagePruned) { reference.find_by(idempotency_key: "second") }
   end
 
+  test "remembers a re-sent key once" do
+    reference = CartActor.ref("alice")
+    reference.async(idempotency_key: "first").checkout(order_id: 1)
+    reference.async(idempotency_key: "second").checkout(order_id: 2)
+    run_actors
+    SolidObjects::Message.delete_all
+    reference.async(idempotency_key: "first").checkout(order_id: 3)
+    run_actors
+
+    assert_equal [ "second", "first" ],
+      SolidObjects::Instance.sole.completed_idempotency_keys
+  end
+
   test "remembers nothing for a message that carried no key" do
     reference = CartActor.ref("alice")
     reference.async.checkout(order_id: 1)