Document Arch release candidate status

[ClaudiuSchuster]

Summary

• record that the clean Arch Cinnamon/X11 gate for 0.8.0-1 is complete
• publish the reviewed package installation route and safety boundary
• keep Arch labeled as a release candidate until configured account, transfer and login-lifecycle review is complete
• remove the personal reviewer reference from public portability documentation

Verification

• git diff --check
• make check
• Super-Linter 8.7.0 with the repository CI profile

This is a documentation-only release-gating follow-up to #66. It does not change the package that passed the clean Arch VM record.