feat: add agentmail skill

[billyshipp]

Type of Change

• Skill - adds a new skill in .claude/skills/

Description

Adds an AgentMail skill that gives NanoClaw agents a dedicated email address using the AgentMail API (https://agentmail.to). AgentMail is an API-first email platform built specifically for AI agents.

What this skill enables

• Create a dedicated agent email inbox (agent@agentmail.to)
• Send emails with rich content and attachments
• Check and read incoming messages via polling
• Email-based workflow automation

NanoClaw-specific improvements over existing OpenClaw AgentMail skill

• No Python/pip required — uses curl directly (pip is not available in NanoClaw containers)
• Polling instead of webhooks — NanoClaw has no inbound webhook gateway, so this skill uses on-demand polling
• Built-in prompt injection protection — instructions for maintaining a trusted sender allowlist and treating email body content as untrusted external data
• No Clawdbot references — all Clawdbot-specific webhook transform instructions removed and replaced with NanoClaw-native patterns

Security

The skill includes detailed guidance on prompt injection risks (anyone can email the agent with fake instructions) and mitigation strategies: trusted sender allowlists, treating email body content as external untrusted data, and never auto-acting on messages from unknown senders.

For Skills

• I have not made any changes to source code
• My skill contains instructions for Claude to follow (not pre-built code)
• I tested this skill on a fresh clone