- Merge the separate custom-providers section into the unified provider
grid; "Custom" in the add-provider picker now acts as an add-new action
(trailing + mark) and opens the dedicated modal, supporting multiple
OpenAI-compatible endpoints
- Simplify the custom provider modal: drop the default-model field, add
an inline delete button, align colors with the theme
- Keep the legacy single "custom" card visible (models page, chat
dropdown and legacy config page) while custom_api_key/custom_api_base
is still in use, so existing single-provider setups don't disappear
- Unify user-facing wording from "vendor" to "provider" in UI and docs
- Restructure custom provider docs (zh/en/ja) around Web console and
config file usage
