docs: say --offline cuts release asset downloads

scripts/generate_pack.py

@@ -2900,7 +2900,9 @@ def _main(held: contextlib.ExitStack) -> None:
     parser.add_argument(
         "--offline",
         action="store_true",
-        help="Skip data directory freshness check, use cache only",
+        help="No network at all: data directories and release assets come "
+        "from the cache only, so a gitignored file never fetched is missing "
+        "(--no-refresh-data keeps the trees as cached and still fetches assets)",
     )
     parser.add_argument(
         "--refresh-data",

scripts/pipeline.py

@@ -330,7 +330,9 @@ def main() -> None:
         "--skip-docs", action="store_true", help="Skip README and site generation"
     )
     parser.add_argument(
-        "--offline", action="store_true", help="Skip data directory refresh"
+        "--offline", action="store_true",
+        help="No network: skips steps 2 to 2b2 and packs only the release "
+        "assets already in .cache/large/"
     )
     parser.add_argument(
         "--output-dir", default="dist", help="Pack output directory (default: dist/)"

tests/test_audit_regressions.py

@@ -4327,5 +4327,22 @@ class EveryOptionIsDocumented(unittest.TestCase):
         self.assertEqual(undocumented, [])
 
 
+
+class OfflineHelpSaysWhatItCuts(unittest.TestCase):
+    """--offline read "Skip data directory freshness check" while it also
+    stops release assets from downloading: on a fresh clone the gitignored
+    files were missing from the pack and nothing had announced it."""
+
+    def test_both_helps_name_the_release_assets(self):
+        for script in ("generate_pack.py", "pipeline.py"):
+            with self.subTest(script=script):
+                out = subprocess.run(
+                    [sys.executable, f"scripts/{script}", "--help"],
+                    capture_output=True, text=True, cwd=str(ROOT), check=True,
+                ).stdout
+                block = out.split("--offline", 2)[-1].split("\n  --", 1)[0]
+                self.assertIn("release", " ".join(block.split()))
+
+
 if __name__ == "__main__":
     unittest.main()