fix: make package existence check distro-aware

check_package_exists was only checking name+version+release, so an
almalinux package already in Gitea would cause fedora builds to be
skipped incorrectly.

Now passes the target distro from PackageInfo through to
check_package_exists, which maps it to an RPM dist suffix (.el9,
.fc43, etc.) and queries the Gitea package files endpoint to confirm
a distro-specific file exists before skipping the build.

Also adds fedora/42, fedora/43, fedora/44 to the allowed repository
values in the metadata schema.

tools/build

@@ -94,7 +94,7 @@ METADATA_SCHEMA = {
                     'minlength': 1,
                     'schema': {
                         'type': 'string',
-                        'allowed': ['almalinux/el8', 'almalinux/el9'],
+                        'allowed': ['almalinux/el8', 'almalinux/el9', 'fedora/42', 'fedora/43', 'fedora/44'],
                         'empty': False
                     }
                 },
@@ -504,17 +504,39 @@ def normalize_version(version: str) -> str:
     return ''.join(normalized_parts)
 
 
-def check_package_exists(package_name: str, version: str, release: str) -> bool:
+def get_rpm_dist_suffix(distro: str) -> str:
+    """
+    Map a distro path to the RPM dist tag suffix used in package filenames.
+
+    Examples:
+        'almalinux/el9' -> '.el9'
+        'fedora/43'     -> '.fc43'
+    """
+    if distro.startswith('almalinux/'):
+        return '.' + distro.split('/', 1)[1]
+    if distro.startswith('fedora/'):
+        return '.fc' + distro.split('/', 1)[1]
+    return ''
+
+
+def check_package_exists(package_name: str, version: str, release: str, distro: str = '') -> bool:
     """
     Check if a package version exists in the Gitea package registry.
 
+    When distro is provided the check is distro-aware: it lists the files
+    attached to the package version and returns True only when a file whose
+    name contains the expected RPM dist suffix (e.g. '.el9', '.fc43') is
+    found.  This prevents a package built for almalinux/el9 from being
+    mistaken for a fedora/43 build (and vice-versa).
+
     Args:
         package_name: Name of the package
         version: Version string
         release: Release number
+        distro: Target distro path (e.g. 'almalinux/el9', 'fedora/43')
 
     Returns:
-        True if package exists, False otherwise
+        True if package exists for the given distro, False otherwise
     """
     logger = logging.getLogger(__name__)
 
@@ -543,10 +565,41 @@ def check_package_exists(package_name: str, version: str, release: str) -> bool:
 
         if response.status_code == 200:
             package_info = response.json()
-            # Package exists if we get package info back
-            exists = bool(package_info.get('id'))
-            logger.debug(f"Package {package_name}:{full_version} {'exists' if exists else 'not found'}")
-            return exists
+            if not package_info.get('id'):
+                logger.debug(f"Package {package_name}:{full_version} not found")
+                return False
+
+            # No distro filter – treat any file as a match
+            if not distro:
+                logger.debug(f"Package {package_name}:{full_version} exists")
+                return True
+
+            # Distro-aware check: inspect individual file names for the dist suffix
+            dist_suffix = get_rpm_dist_suffix(distro)
+            if not dist_suffix:
+                logger.debug(f"Package {package_name}:{full_version} exists (no dist suffix for {distro})")
+                return True
+
+            files_url = f"{base_url}/api/v1/packages/{owner}/{package_type}/{package_name}/{full_version}/files"
+            logger.debug(f"Checking distro-specific files: {files_url}")
+            files_response = requests.get(files_url, headers=headers, timeout=30)
+
+            if files_response.status_code == 200:
+                files = files_response.json()
+                for file_info in files:
+                    if dist_suffix in file_info.get('name', ''):
+                        logger.debug(f"Package {package_name}:{full_version} exists for {distro}")
+                        return True
+                logger.debug(f"Package {package_name}:{full_version} not found for {distro} (no {dist_suffix} file)")
+                return False
+            else:
+                # If files endpoint fails fall back to treating version existence as a match
+                logger.warning(
+                    f"Could not list files for {package_name}:{full_version}: "
+                    f"{files_response.status_code} – assuming package exists"
+                )
+                return True
+
         elif response.status_code == 404:
             logger.debug(f"Package {package_name}:{full_version} not found (404)")
             return False
@@ -1449,7 +1502,8 @@ class Builder:
                 if check_package_exists(
                     package_info.name,
                     package_info.version,
-                    package_info.release
+                    package_info.release,
+                    package_info.distro
                 ):
                     self.logger.info(
                         f"Skipping {package_info} (already exists in repository)"