Update v0.1.2 post-release status docs

[willamhou]

Summary

• record the completed v0.1.2 Release Matrix run and GHCR manifest digest
• clarify npm/Homebrew publish skips due missing credentials
• replace the stale next-release smoke wording with clean-machine release-smoke follow-up

Checks

• git diff --check
• node scripts/check-secrets.js

[github-actions]

DeepSeekCode review of PR #23 (Update v0.1.2 post-release status docs)

Let me examine the PR diff by fetching the remote branch and comparing it.