Skip ripgrep apt install when rg is already available on custom runners

[strawgate]

Problem

The generated Copilot agent job unconditionally runs:

- name: Install ripgrep
  run: sudo apt-get update -qq && sudo apt-get install -y -qq ripgrep

Many custom/full runner images already include rg. Those jobs still update apt metadata, hit package infrastructure, and perform a privileged package-manager operation on every run.

This is emitted by gh-aw v0.85.4 before checkout for workflows using the Copilot engine; it is generated output, so consumers cannot cleanly optimize the step without patching lock files.

Suggested behavior

Probe first and install only when needed, for example:

if command -v rg >/dev/null 2>&1; then
  rg --version
else
  sudo apt-get update -qq
  sudo apt-get install -y -qq ripgrep
fi

This preserves compatibility with minimal runner images while avoiding redundant network and package-manager work on pre-baked images.