Registry: the description fits its 1000 byte limit

The 2.8.0 upload was refused with "description is too long": naming
Image Folder and Callout took the description to 1024 bytes and the
Registry takes 1000. It is 989 now, and release_preflight.py fails on a
description over the limit, so this is caught before a version lands.

The Registry's scan also warned about two statements on one line in
tests/test_image_folder.py and says that becomes an error. They are two
lines now.

scripts/release_preflight.py

@@ -59,6 +59,17 @@ if match:
 else:
     errors.append('pyproject.toml has no version = "..." line')
 
+# The Registry refuses an upload whose description is over 1000 bytes
+# ("description is too long"), and it says so only after the version is
+# on main.
+DESCRIPTION_LIMIT = 1000
+match = re.search(rb'^description\s*=\s*"([^"]*)"', raw, re.MULTILINE)
+if match and len(match.group(1)) > DESCRIPTION_LIMIT:
+    errors.append(
+        f"the pyproject description is {len(match.group(1))} bytes; "
+        f"the Registry takes {DESCRIPTION_LIMIT} at most"
+    )
+
 # --- 2. the frontend version constant matches --------------------------------
 js_version = None
 try: