Tell scheduling apart from unpublishing in the history

Giving a record a future date was recorded as "unpublished", and announced
to webhooks as such. The history now compares before and after.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/Feature/Api/ReviewAndHistoryApiTest.php

@@ -158,6 +158,10 @@ class ReviewAndHistoryApiTest extends TestCase
             ->assertJsonPath('data.awaiting_review', false)
             ->assertJsonPath('data.published_at', $at->toIso8601String());
 
+        // A date in the future is neither live nor taken down, and the
+        // history says so.
+        $this->assertSame('scheduled', $project->revisions()->first()->event);
+
         $this->postJson("/api/v1/projects/{$project->id}/unpublish")
             ->assertOk()
             ->assertJsonPath('data.published_at', null);