fix(kimi-code): correct maxTokens defaults and add server-side override (#1217)

* fix(kimi-code): correct maxTokens defaults and add server-side override

Fixes #1215

- Update kimiCodeDefaultModelInfo.maxTokens from 32768 to 131072

- Add kimiCodeModelDefaults for per-model fallback values

- Add max_tokens to kimiCodeModelSchema for server response parsing

- Override maxTokens in mapKimiCodeModel: server > model-default > global-default

- Add 4 new tests for maxTokens override and fallback behavior

* refactor(kimi-code): address PR review comments

- Replace production constant imports in tests with hardcoded fixture values

- Add .int() validation to max_tokens Zod schema

- Add fractional max_tokens rejection test

- Export kimiCodeModelSchema for test access

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Co-authored-by: Zoo (VP) <zoo@emebala.dev>