### What does this PR do?
add gemini code assistant config. The example code reviews are in
https://github.com/eric-haibin-lin/verl/pull/17#pullrequestreview-2977403886.
The threshold is set to high to avoid too many review comments.
### Checklist Before Starting
- [x] Search for similar PRs. Paste at least one query link here: ...
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- `{modules}` include `fsdp`, `megatron`, `sglang`, `vllm`, `rollout`,
`trainer`, `ci`, `training_utils`, `recipe`, `hardware`, `deployment`,
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`env`, `tool`, `ckpt`, `doc`, `data`
- If this PR involves multiple modules, separate them with `,` like
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- If this PR breaks any API (CLI arguments, config, function signature,
etc.), add `[BREAKING]` to the beginning of the title.
- Example: `[BREAKING][fsdp, megatron] feat: dynamic batching`
### Checklist Before Submitting
> [!IMPORTANT]
> Please check all the following items before requesting a review,
otherwise the reviewer might deprioritize this PR for review.
- [x] Read the [Contribute
Guide](https://github.com/volcengine/verl?tab=readme-ov-file#contribution-guide).
- [x] Apply [pre-commit
checks](https://github.com/volcengine/verl?tab=readme-ov-file#code-linting-and-formatting):
`pre-commit install && pre-commit run --all-files --show-diff-on-failure
--color=always`
- [ ] Add / Update [the
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