Handle missing uv gracefully

[CybotTM]

Problem

When uv (the Python package manager) is not installed, scripts that depend on it fail without a helpful error message. The agent or user sees cryptic errors instead of clear guidance on how to install uv.

Expected Behavior

When uv is missing:

1. Detect that uv is not available
2. Show a clear error message explaining uv is required
3. Provide installation instructions for common platforms:

   # macOS/Linux
   curl -LsSf https://astral.sh/uv/install.sh | sh
   
   # Windows
   powershell -c "irm https://astral.sh/uv/install.ps1 | iex"
   
   # Or via pip
   pip install uv

Current Behavior

Scripts fail with errors like:

• command not found: uv
• Or the script proceeds and fails later with confusing errors

Suggested Solution

Add a check at the start of scripts or in the toolset initialization:

if ! command -v uv &> /dev/null; then
    echo "Error: uv is required but not installed."
    echo ""
    echo "Install uv:"
    echo "  curl -LsSf https://astral.sh/uv/install.sh | sh"
    echo ""
    echo "See: https://docs.astral.sh/uv/"
    exit 1
fi

Or handle it in the CLI toolset's dependency checking mechanism.