Rowan v0.3.1

Documentation and packaging only; scanning behaviour is unchanged.

• Install docs use pipx or uv tool; a bare pip install fails on
  Homebrew and other externally managed Pythons.
• Getting started explains how to add an LLM for rowan hunt (Ollama,
  DeepSeek or OpenRouter), and the usage guide lists every backend env var.
• The GitHub Action has a fuller description for its Marketplace listing,
  and its docs show the security-events: write permission it needs.

Install: pipx install rowan-sast (see the getting started guide).