Closes (#1817)
<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Fixes the bug where editing a custom model didn’t update the currently
selected model. The selection now stays in sync after renaming or
editing.
- **Bug Fixes**
- Use useSettings to detect if the edited model is the active one (match
provider and apiName).
- Update settings.selectedModel with the new apiName; on failure show an
error and keep the dialog open; otherwise show success, call onSuccess,
then close.
<sup>Written for commit 88045165a3989277e703a8f31712fcf1dfeaa32a.
Summary will update automatically on new commits.</sup>
<!-- End of auto-generated description by cubic. -->
Now users can free to edit their custom models by double clicking any
custom models created in each provider.
Before this, they have to delete -> create a new one.
I simply add an edit panel (which looks the same as 'Add Custom Model')
and integrate that process into the "update" button.
There is one more issue that if a user deletes a model that he was using
in chat, then back to chat, that model would still appear (and work)
unless user chooses a new one.
Tried to modify "delete-custom-model" in language_model_handlers.ts by
the logic that if the name of that model matches the latest using one ->
switch to auto (or default) model. Yet I failed, maybe need more
explanation for this :)
