Python 3.14 Throws a Runtime exception

[reinecke]

As reported in this thread, OTIO in python 3.14 on macos arm64 throws a runtime error loading .otio files:

File "/Users/al/Library/Python/3.14/lib/python/site-packages/opentimelineio/adapters/__init__.py", line 94, in from_filepath
   return plugins.ActiveManifest().from_filepath(outext)
       ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/al/Library/Python/3.14/lib/python/site-packages/opentimelineio/plugins/manifest.py", line 332, in ActiveManifest
   _MANIFEST = load_manifest()
  File "/Users/al/Library/Python/3.14/lib/python/site-packages/opentimelineio/plugins/manifest.py", line 317, in load_manifest
   plugin_manifest = manifest_from_file(builtin_manifest_path)
  File "/Users/al/Library/Python/3.14/lib/python/site-packages/opentimelineio/plugins/manifest.py", line 49, in manifest_from_file
   result = core.deserialize_json_from_file(filepath)
RuntimeError: bad any cast

It is reported the same thing works fine on linux.

This should be addressed and we should enable CI for python 3.14.