[PDF Skill] macOS: dependency install guidance should default to venv, not system `python -m pip`

I was suggested by @etraut-openai to open an issue using the feedback mechanism

Summary

On macOS, Codex sometimes suggests commands like python -m pip install ... that target system/global Python.
This often fails (permissions / externally-managed environment) and is not a reliable default.
The guidance should default to creating and using a virtual environment first.

Environment

• OS: macOS (reproducible across setups)
• Tooling: Codex CLI / agent workflow
• Typical failing pattern: python -m pip install ... without an active venv

Steps to Reproduce

1. Ask Codex to install Python dependencies (example: reportlab, pdfplumber, pypdf).
2. Codex suggests or runs python -m pip install ... directly.
3. Install attempts to write to system package directories.
4. Command fails due to permission/external-management constraints.

Actual Behavior

Codex proposes system-level pip installs as a fallback path.

Expected Behavior

Codex should prefer:

1. python3 -m venv <path>
2. source <path>/bin/activate
3. python -m pip install -U pip
4. python -m pip install <packages>

Optional: if uv is used, still require an active venv for package installation.

Why this matters

This is a common macOS failure mode and not environment-specific.
Defaulting to venv-based installs would prevent recurring setup failures and reduce user friction.

Proposed Fix

Update built-in install guidance (skills/prompts/docs) so Python dependency instructions always use isolated environments first, and avoid system Python installs by default.