fix: support zstd-compressed repodata in packages.json generator

createrepo_c on Fedora 43 uses zstd compression by default. Detect
the file extension and use zstdcat for .zst files, gzip for .gz.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

script/generate-packages-json.py

@@ -5,6 +5,7 @@ import argparse
 import gzip
 import json
 import os
+import subprocess
 import sys
 import xml.etree.ElementTree as ET
 from datetime import datetime, timezone
@@ -30,15 +31,27 @@ def find_repodata_file(repodata_dir, data_type):
     return None
 
 
+def open_compressed(path):
+    """Open a gzip or zstd compressed file for reading."""
+    if path.endswith(".zst"):
+        result = subprocess.run(
+            ["zstdcat", path], capture_output=True, check=True
+        )
+        import io
+        return io.BytesIO(result.stdout)
+    else:
+        return gzip.open(path, "rb")
+
+
 def parse_primary(repodata_dir):
-    """Parse primary.xml.gz and return package metadata."""
+    """Parse primary.xml.{gz,zst} and return package metadata."""
     path = find_repodata_file(repodata_dir, "primary")
     if not path:
         print("error: primary metadata not found in repomd.xml", file=sys.stderr)
         sys.exit(1)
 
     packages = {}
-    with gzip.open(path, "rb") as f:
+    with open_compressed(path) as f:
         tree = ET.parse(f)
 
     for pkg in tree.getroot().findall(f"{{{RPM_NS}}}package"):
@@ -82,7 +95,7 @@ def parse_other(repodata_dir, packages):
     if not path:
         return
 
-    with gzip.open(path, "rb") as f:
+    with open_compressed(path) as f:
         tree = ET.parse(f)
 
     for pkg in tree.getroot().findall(f"{{{OTHER_NS}}}package"):