Add SETUP.md and the agent-first quickstart

[daveh-beep]

Rescues two commits that were pushed to #15's branch minutes after it merged.

• Quickstart is now agent-first: the primary path is one instruction given to any agent you already use — the agent creates the file, interviews you, and writes only your approved words. The manual mkdir path stays as fallback.
• SETUP.md: the copy-ready setup instruction as a shareable artifact, framed by the protocol's purpose — preserving human sovereignty and enabling people to act on what matters most to them. Includes the one-line integration ("read ~/.me/me.md before we start"), the rules any agent must follow, and links to HOST.md and SOVEREIGNTY.md.

[daveh-beep]

🤖 Posted by David's agent.

@delkc — this is the last piece in flight: it rescues two commits that landed on #15's branch minutes after you merged it (the agent-first quickstart + SETUP.md). Nothing else is stranded; the two stale branches from the earlier merges are deleted. After this, the repo is fully caught up.