Add a way to delete custom providers from configuration

[MuoDoo]

Problem

Open Code Review currently supports adding and updating custom providers through ocr config provider and ocr config set custom_providers.<name>.<field> <value>, but there does not appear to be a supported way to delete a custom provider once it has been saved.

Users currently need to manually edit ~/.opencodereview/config.json and remove the corresponding custom_providers.<name> entry. If the deleted custom provider is also the active provider, they also need to manually clear or change provider to avoid configuration resolution errors.

Current Behavior

• ocr config supports provider, model, and set.
• ocr config set custom_providers.<name>.<field> <value> creates or updates custom provider fields.
• The Custom tab in ocr config provider supports selecting existing custom providers and adding new ones.
• There is no documented delete, remove, unset, or equivalent command for custom providers.

Expected Behavior

Provide a supported way to delete custom providers.

A TUI-based deletion flow may be preferable, since custom providers are primarily managed through ocr config provider. We should also investigate how OpenCode handles provider deletion/removal in its TUI before finalizing the interaction design.

Possible approaches:

• Add a delete action in the Custom tab of ocr config provider, for example pressing d on a selected custom provider and confirming deletion.
• Optionally also add a non-interactive command, for example:

  ocr config delete custom_providers.<name>

  or:

  ocr config unset custom_providers.<name>

When deleting the currently active provider, the command should either:

• clear the active provider and related fallback model, or
• require confirmation and guide the user to select another provider.

Acceptance Criteria

• Users can delete a saved custom provider without manually editing ~/.opencodereview/config.json.
• Deleting the active provider leaves the config in a valid state or provides a clear error/confirmation flow.
• Tests cover deleting an inactive custom provider and deleting the currently active custom provider.
• README/docs mention the supported deletion workflow.

[Ackberry]

Hello @MuoDoo , I would like to take this issue!

[lizhengfeng101]

Hi @Ackberry, thanks for picking this up! We've been realizing this is a real gap in the UX — users shouldn't have to hand-edit config files to remove a provider. Really looking forward to your PR!

[Ackberry]

Awesome. Thanks!