fix: validate top-level registry structure in get() and restore()

- get() now validates self.data["presets/extensions"] is a dict before accessing
- restore() ensures presets/extensions dict exists before writing
- Prevents crashes when registry JSON is parseable but has corrupted structure
- Applied same fixes to both PresetRegistry and ExtensionRegistry for parity

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: iamaeroplane

src/specify_cli/extensions.py

@@ -302,6 +302,9 @@ def restore(self, extension_id: str, metadata: dict):
         """
         if metadata is None or not isinstance(metadata, dict):
             raise ValueError(f"Cannot restore '{extension_id}': metadata must be a dict")
+        # Ensure extensions dict exists (handle corrupted registry)
+        if not isinstance(self.data.get("extensions"), dict):
+            self.data["extensions"] = {}
         self.data["extensions"][extension_id] = copy.deepcopy(metadata)
         self._save()
 
@@ -327,7 +330,10 @@ def get(self, extension_id: str) -> Optional[dict]:
         Returns:
             Deep copy of extension metadata, or None if not found or corrupted
         """
-        entry = self.data["extensions"].get(extension_id)
+        extensions = self.data.get("extensions")
+        if not isinstance(extensions, dict):
+            return None
+        entry = extensions.get(extension_id)
         # Return None for missing or corrupted (non-dict) entries
         if entry is None or not isinstance(entry, dict):
             return None

src/specify_cli/presets.py

@@ -322,6 +322,9 @@ def restore(self, pack_id: str, metadata: dict):
         """
         if metadata is None or not isinstance(metadata, dict):
             raise ValueError(f"Cannot restore '{pack_id}': metadata must be a dict")
+        # Ensure presets dict exists (handle corrupted registry)
+        if not isinstance(self.data.get("presets"), dict):
+            self.data["presets"] = {}
         self.data["presets"][pack_id] = copy.deepcopy(metadata)
         self._save()
 
@@ -337,7 +340,10 @@ def get(self, pack_id: str) -> Optional[dict]:
         Returns:
             Deep copy of preset metadata, or None if not found or corrupted
         """
-        entry = self.data["presets"].get(pack_id)
+        packs = self.data.get("presets")
+        if not isinstance(packs, dict):
+            return None
+        entry = packs.get(pack_id)
         # Return None for missing or corrupted (non-dict) entries
         if entry is None or not isinstance(entry, dict):
             return None