Implement independent format gates for release workflow (issue #86)

Add XBPS build and sign steps to CI workflow
Add XBPS publication as independent gate (requires manual trigger)
Track format availability in release notes
Update release-footer.md with XBPS install instructions
Add --available/--withheld arguments to extract_changelog.py
Attach XBPS artifacts to Gitea release
Clean up XBPS signing key material after use

scripts/extract_changelog.py

@@ -68,6 +68,20 @@ def assemble_release_body(section: str, footer: str) -> str:
     return f"{section}{separator}{footer}"
 
 
+def format_availability_section(
+    available: list[str], withheld: list[str]
+) -> str:
+    """Generate a package formats section for release notes."""
+    if not available and not withheld:
+        return ""
+    lines = ["\n## Package formats\n"]
+    if available:
+        lines.append(f"Available: {', '.join(available)}")
+    if withheld:
+        lines.append(f"Withheld: {', '.join(withheld)}")
+    return "\n".join(lines)
+
+
 def main(argv: list[str] | None = None) -> int:
     parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument("changelog", type=Path)
@@ -77,6 +91,18 @@ def main(argv: list[str] | None = None) -> int:
         type=Path,
         help="append this standing release guidance after the extracted section",
     )
+    parser.add_argument(
+        "--available",
+        action="append",
+        default=[],
+        help="format available for this release (can be repeated)",
+    )
+    parser.add_argument(
+        "--withheld",
+        action="append",
+        default=[],
+        help="format withheld from this release (can be repeated)",
+    )
     args = parser.parse_args(argv)
     try:
         section = extract_changelog(args.changelog, args.version)
@@ -88,6 +114,10 @@ def main(argv: list[str] | None = None) -> int:
                     f"cannot read release footer {args.footer}: {error.strerror}"
                 ) from error
             section = assemble_release_body(section, footer)
+        if args.available or args.withheld:
+            formats = format_availability_section(args.available, args.withheld)
+            if formats:
+                section = f"{section}\n{formats}"
         sys.stdout.write(section)
     except ChangelogError as error:
         print(f"::error::{error}", file=sys.stderr)