On top of the salvaged PR #12505 (Jason/farion1231, which adds dict-format
models: enumeration to both sections), three section-3 refinements from
competing PR #11534 (YangManBOBO):
- accept base_url as canonical (matches Hermes's writer and custom_providers
entries); keep api/url as fallbacks for legacy/hand-edited configs
- accept singular model as a default_model synonym, matching custom_providers
- add seen_slugs guard so the same provider slug appearing in both
providers: dict and custom_providers: list emits exactly one picker row
(providers: dict wins since section 3 runs first)
Two regression tests cover the new behavior. AUTHOR_MAP entry added for
farion1231 so CI doesn't reject the cherry-picked commit.
5a23f3291a