Invalid channel on comfy 0.15

[ComfyUI 0.15.1]
[ComfyUI_frontend v1.39.19]

OS
linux
Python Version
3.12.3 (main, Mar 3 2026, 12:15:18) [GCC 13.3.0]

```
[ComfyUI-Manager] default cache updated: https://api.comfy.org/nodes
[ComfyUI-Manager] An invalid channel was used: https://raw.githubusercontent.com/ltdrdata/ComfyUI-Manager/main
Exception in thread Thread-1 ():
Traceback (most recent call last):
File "/usr/lib/python3.12/threading.py", line 1073, in _bootstrap_inner
self.run()
File "/usr/lib/python3.12/threading.py", line 1010, in run
self._target(*self._args, **self._kwargs)
File "/mnt/data1/development/ComfyUI/custom_nodes/comfyui-manager/glob/manager_server.py", line 1863, in
threading.Thread(target=lambda: asyncio.run(default_cache_update())).start()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.12/asyncio/runners.py", line 194, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "/usr/lib/python3.12/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.12/asyncio/base_events.py", line 687, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "/mnt/data1/development/ComfyUI/custom_nodes/comfyui-manager/glob/manager_server.py", line 1858, in default_cache_update
await core.unified_manager.get_custom_nodes(channel_url, 'remote')
File "/mnt/data1/development/ComfyUI/custom_nodes/comfyui-manager/glob/manager_core.py", line 885, in get_custom_nodes
nodes = await self.load_nightly(channel, mode)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/data1/development/ComfyUI/custom_nodes/comfyui-manager/glob/manager_core.py", line 855, in load_nightly
raise InvalidChannel(channel_url)
manager_core.InvalidChannel: https://raw.githubusercontent.com/ltdrdata/ComfyUI-Manager/main
```

Start in glob/manager_server.py at default_cache_update and follow the call into glob/manager_core.py, especially get_custom_nodes and load_nightly. Reproduce the logged channel URL and trace why it reaches InvalidChannel; done should mean the intended handling of this invalid-channel failure is established and addressed.

Written by the indexing model from the issue text.