opencode >=1.14 freezes output.args via Immer before plugin hooks run.
Direct property assignment or Object.assign on a frozen object throws
TypeError. This helper replaces output.args with a shallow clone
containing the patch, avoiding mutation of the frozen original.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
YeonGyu-Kim