fix: raise on a registry missing a platform file

list_registered_platforms skipped a registered platform whose YAML was missing and returned an empty list without a registry. verify --all --strict, every --all build, the CI matrix and the site then ran over fewer platforms and exited 0, and install.py kept serving the stale manifest. Both now raise and name the file.

scripts/common.py

@@ -411,10 +411,14 @@ def list_registered_platforms(
 
     Only registered platforms generate packs and appear in CI.
     Unregistered YAMLs (e.g., emulatorjs.yml) are base configs for inheritance.
+
+    A missing registry, or a registered platform whose file is gone, raises:
+    left out quietly, verify --all --strict and every --all build passed
+    having checked none of it, and install.py kept serving its last manifest.
     """
     registry_path = os.path.join(platforms_dir, "_registry.yml")
     if not os.path.exists(registry_path):
-        return []
+        raise FileNotFoundError(f"no platform registry at {registry_path}")
     with open(registry_path) as f:
         registry = yaml_load(f) or {}
     platforms = []
@@ -423,8 +427,11 @@ def list_registered_platforms(
         if status == "archived" and not include_archived:
             continue
         config_path = os.path.join(platforms_dir, meta.get("config", f"{name}.yml"))
-        if os.path.exists(config_path):
-            platforms.append(name)
+        if not os.path.exists(config_path):
+            raise FileNotFoundError(
+                f"{name} is registered in {registry_path} but {config_path} does not exist"
+            )
+        platforms.append(name)
     return platforms