fix(discourse): enable allow_uncategorized_topics in admin bootstrap so create-topic POST succeeds (Discourse 3.x 422 'Category cant be blank')

tests/discourse/functional/_discourse.py

@@ -24,7 +24,13 @@ from harness import lifecycle  # noqa: E402
 # Rails snippet (single line): find-or-create an admin, create an ApiKey, print key + username as the
 # last two lines. SecureRandom is available in the Rails runtime. We mark the user active + approved
 # so the API accepts it. created_by_id must be set (ApiKey validates it).
+#
+# We also enable `allow_uncategorized_topics` (a standard Discourse feature, off by default since 3.x):
+# without it, POST /posts.json with no category 422s "Category can't be blank". This is config parity
+# with a real forum (the operator would either enable uncategorized or pick a category), not a test
+# weakening — the create-topic round-trip still posts a real topic and asserts a unique marker survives.
 _BOOTSTRAP_RB = (
+    "SiteSetting.allow_uncategorized_topics = true; "
     "u = User.where(admin: true).order(:id).first; "
     "if u.nil?; "
     "u = User.create!(username: 'ccciadmin', name: 'CCCI Admin', "