MiniMax descriptors carried thinkingFormat: "zai", which made
openai-completions emit thinking: { type: "enabled" } in plan mode.
MiniMax's OpenAI-compatible endpoint rejects that field with
`400 invalid params, invalid chat setting (2013)`. Drop thinkingFormat
from both minimax-coding-plan descriptors and add
supportsReasoningEffort: false (MiniMax also ignores reasoning_effort).
Normalize bundled minimax-code/minimax-code-cn entries inside
applyGeneratedModelPolicy so a regenerated models.json cannot
reintroduce the bad flag.
Fixes#955
can1357
4e8d69076d