Lesson.order from the book (seed sets it, also re-syncs unit/node order); matrix lesson rows as one multi-line step

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

content/migrations/0025_lesson_order.py

@@ -0,0 +1,22 @@
+# Generated by Django 5.2.17 on 2026-10-15 10:16
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('content', '0024_explicit_ordering'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='lesson',
+            options={'ordering': ['order', 'id']},
+        ),
+        migrations.AddField(
+            model_name='lesson',
+            name='order',
+            field=models.PositiveIntegerField(default=10000),
+        ),
+    ]