Add x402 Agent Mail service and autonomous domain activation

[Svaag]

Summary

• add an API-only Agent Mail product with x402 activation and paid sends
• add hosted-domain, managed-domain, and atomic domain-plus-mail provisioning
• add mailbox messages, attachment retrieval, events, signed webhooks, quotas, retention, recovery, and lifecycle workers
• add anonymous agent domain purchasing with capability-based order access
• publish Bazaar/OpenAPI discovery metadata and Agent Skills for mail and customer journeys

Why

The customer campaign needs a concrete agent-native email identity outcome: an agent can acquire a domain, activate a mailbox, prove controlled send/receive, and diagnose delivery failures without a human account or subscription checkout.

Product impact

• activation is $1 for 30 days with no automatic renewal
• outbound sends are $0.01, limited to one recipient, 20 sends/day, and 5 new recipients/day
• the service remains API-only: no SMTP submission, IMAP, POP, or webmail
• payment handoff and provisioning are recoverable, while capabilities and backend credentials remain encrypted and out of payment metadata

Rollout

The API is fail-closed until the related infrastructure and product launch gates are approved. Production customer-result examples remain pending real canaries.

Related PRs

• Web campaign: Add outcome-led x402 customer journey campaign hyrule-web#43
• Staged infrastructure: Stage dedicated Agent Mail infrastructure network-operations#467

Validation

• uv run pytest -q — 500 passed
• uvx ruff check .
• uv run mypy hyrule_cloud — 102 source files
• both new Agent Skills pass the skill validator