docs: simplify quickstart install

[TacoRocket]

Summary

• make pip install azurefox the first and most obvious Quickstart step
• move the --outdir explanation below the install block so the install path stays simple
• keep the virtualenv example as an optional follow-up instead of the primary path

Validation

• docs-only change
• git push pre-push guardrail (lint + pytest -m "not integration")