grep tool times out on large repos before returning any results

### Describe the bug

When using the built in grep tool in a large mono repo, the tool returns "timeout" with no results. I had to instruct copilot to use ripgrep rg, instead.

### Affected version

GitHub Copilot CLI 1.0.36

### Steps to reproduce the behavior

1. Open Copilot CLI in a large monorepo
2. Ask to search for a pattern across a folder and its subdirectories, dont nudge it to use ripgrep yet
3. It'll start grepping and maybe timeout

### Expected behavior

The grep tool should return results (even partial) within a reasonable time

### Additional context

_No response_

Comece localizando a ferramenta grep integrada usada pelo Copilot CLI e reproduza a busca descrita na issue em um monorepo grande. Compare seu comportamento com o ripgrep e verifique se as buscas retornam resultados, incluindo resultados parciais quando apropriado, dentro de um tempo razoável.

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