When a built-in provider model has reasoning:true (e.g. MiniMax-M2.5) and
the user explicitly sets reasoning:false in their config, mergeProviderModels
unconditionally overwrote the user's value with the built-in catalog value.
The merge code refreshes capability metadata (input, contextWindow, maxTokens,
reasoning) from the implicit catalog. This is correct for fields like
contextWindow and maxTokens — the catalog has authoritative values that
shouldn't be stale. But reasoning is a user preference, not just a
capability descriptor: users may need to disable it to avoid 'Message
ordering conflict' errors with certain models or backends.
Fix: check whether 'reasoning' is present in the explicit (user-supplied)
model entry. If the user has set it (even to false), honour that value.
If the user hasn't set it, fall back to the built-in catalog default.
This allows users to configure tools.models.providers.minimax.models with
reasoning:false for MiniMax-M2.5 without being silently overridden.
Fixes#25244
b863316e7b