Add project schema version

clips/models.py

@@ -199,14 +199,14 @@ class Block(models.Model):
 class Project(models.Model):
     """Tier 1: the document's root.
 
-    `seq` is the monotonic project version docs/architecture.md asks for. Every
-    write bumps it, and a client that sees `seq > local + 1` refetches — which is
-    what makes staleness self-healing rather than permanent once there is a
-    broadcast to miss.
+    `schema_version` identifies the stored document format. `seq` counts writes
+    to this particular project; it is not a format version. Every write bumps
+    `seq`, and a client that sees `seq > local + 1` refetches once broadcasts exist.
     """
 
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     name = models.CharField(max_length=200, default="untitled")
+    schema_version = models.PositiveIntegerField(default=1)
     seq = models.PositiveBigIntegerField(default=0)
     palette = models.CharField(max_length=64, default="arthur/default")
     created = models.DateTimeField(auto_now_add=True)