Codex caught a regression: the contributor's _runtime_preferred_base_url preferred
the runtime base_url for ALL non-custom providers, which would clobber an explicit
providers.<id>.base_url override pointing at a different host/port (LM Studio at a
LAN IP, an OpenRouter mirror). Now only prefer the runtime URL when it's the SAME
scheme+host+port as the configured one (the #3895 /v1-dedup case is path-only on
the same host); a genuinely different configured endpoint wins. Added
_same_base_url_endpoint() + 2 regression tests (different-endpoint preserved,
same-endpoint normalization).
nesquena-hermes