fix(extensions): validate hooks is a dict and restrict alias 3-part correction to ext_id (#2017)

- Raise ValidationError with a clear message if the manifest 'hooks' value
  is not a mapping (previously would AttributeError on .items())
- Restrict _try_correct_alias_name 3-part correction (speckit.X.Y → X.Y)
  to only apply when X == ext_id; when X differs the alias is squatting a
  foreign namespace and should be rejected, not silently rewritten

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: iamaeroplane

src/specify_cli/extensions.py

@@ -248,7 +248,12 @@ def _validate(self):
                         )
 
         # Rewrite any hook command references that pointed at a renamed command.
-        for hook_name, hook_data in self.data.get("hooks", {}).items():
+        hooks = self.data.get("hooks", {})
+        if not isinstance(hooks, dict):
+            raise ValidationError(
+                f"'hooks' must be a mapping, got {type(hooks).__name__}"
+            )
+        for hook_name, hook_data in hooks.items():
             if isinstance(hook_data, dict) and hook_data.get("command") in rename_map:
                 old_ref = hook_data["command"]
                 hook_data["command"] = rename_map[old_ref]
@@ -294,7 +299,7 @@ def _try_correct_alias_name(name: str, ext_id: str) -> Optional[str]:
             candidate = f"{ext_id}.{parts[1]}"
             if EXTENSION_ALIAS_PATTERN.match(candidate):
                 return candidate
-        if len(parts) == 3 and parts[0] == 'speckit':
+        if len(parts) == 3 and parts[0] == 'speckit' and parts[1] == ext_id:
             candidate = f"{parts[1]}.{parts[2]}"
             if EXTENSION_ALIAS_PATTERN.match(candidate):
                 return candidate