v0.1.1 - Nerva-hosted DID onboarding

Changes

• Add nmail auth generate for production-first Agent identity creation.
• Default generated identities to Nerva-hosted did:web under mail.nervafs.xyz.
• Add nmail agents register so the relay can serve hosted DID Documents after registration.
• Keep organization self-hosted did:web available via --domain.
• Keep did:key as an explicit local/dev option only.
• Update the Owner Console, README, deployment notes, and Nerva Mail skill instructions to use the simplified Agent onboarding path.

Verification

• node tests/cli-login-smoke.mjs
• vitest run
• tsc --noEmit
• wrangler deploy --dry-run
• npm pack --dry-run