[jrcruciani]

Scope

Item06 (P2) only. Based on main 6f6979f92d9d5bd5ea8177c7311538ae30d89caa, including merged item05. Documentation only; no code, LICENSE, main-checkout or later-item changes.

Changes

• Add docs/MODES.md: Mode A on-box agent and Mode B workstation/separate-VM config-clone workflow.
• Separate human-reviewed proposal-only transfer into the protected target repo from the explicitly human-operated nixos-rebuild --target-host root@host --build-host localhost procedure. No remote receiver or target-host support is claimed for aether-apply.
• Keep guarded target activation restricted to apply, human-only confirmation/token, fresh independent SSH checks, delayed R3 commits, completed rollback and repository/running-system equality before another request.
• Explain local-agent versus target-side supervision, manual activation/recovery races and the stronger need for independent rescue.
• Add narrow README/playbook Known limits/prompt links and one item06 changelog paragraph. Prompt exposes no new privileged agent interface.

Evidence

• Walked through guarded and manual success/failure flows against the current hardening, rescue and helper contract; checked upstream rebuild argument/local-build behavior.
• Checked all 25 local links/anchors in changed documents; all 5 new shell blocks pass bash -n; checked manual phase ordering and git diff --check.
• No operational commands were executed, and no remote deployment, live-host test or VM rerun is claimed.

Parent session coordinates integration/merge; this PR does not merge itself.