When a custom_providers entry in config.yaml has a 'name' field (e.g. 'Agent37'),
the web UI model picker now uses that name as the group header instead of the
generic 'Custom' label.
Previously all custom_providers entries were bucketed under 'custom' which
rendered as 'Custom' in the dropdown optgroup — losing the named identity the
user set up during onboarding.
Changes:
- Track named custom providers as 'custom:<slug>' keys internally so multiple
named providers can coexist as separate groups
- When building model groups, emit each named provider under its own display
name (e.g. 'Agent37') rather than falling through to the generic label
- Unnamed entries (no 'name' field) still fall back to the 'Custom' group
- When all entries are named, the bare 'Custom' bucket is suppressed
Adds 7 tests covering single named provider, multiple named providers,
multiple models in same named provider, unnamed fallback, and mixed cases.
Fixes#557
3e1ba1b783