I5: Fresh-machine dry-run doctor smoke doc for macOS and Linux #187

Problem

onibi doctor --release --after-upgrade exists (per README + doctor.go). But the end-to-end fresh-machine walkthrough — "run these commands on a stock macOS install and verify everything works" — is not documented.

Files

• New docs/fresh-machine-smoke.md
• Reference existing scripts/release-smoke.sh if applicable
• Update docs/getting-started.md with pointer

Content

• Fresh macOS setup (assumes Homebrew present or manual brew install)
• Fresh Debian/Ubuntu setup (assumes user account, no root)
• Steps: install → hooks install → up → doctor → uninstall
• Expected doctor output at each step
• Screenshots of each state

Acceptance

• Doc renders
• Two-platform coverage
• Every step verified on a real machine (or VM)
• Doctor output captured
• Reference from README + docs/release.md

Verification

• Run through the doc on a stock Ubuntu 24.04 VM + fresh macOS 14+ user; every step passes

Context

2026-07 audit — closes release-readiness gap.