docs(cli): add README with usage guide and agent workflow

packages/cli/README.md

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+# MoeMail CLI
+
+Agent-first CLI for MoeMail temporary email service
+
+## Install
+
+```bash
+npm i -g moemail-cli
+```
+
+## Quick Start
+
+### 1. Configure default domain
+```bash
+moemail config --domain moemail.app
+```
+
+### 2. Create a temporary email
+```bash
+moemail create --expiry 1h
+```
+
+### 3. Wait for messages
+```bash
+moemail wait --email-id <email_id> --timeout 120
+```
+
+## Command Reference
+
+| Command | Description | Key Flags |
+|---------|-------------|-----------|
+| `config` | Set default domain and options | `--domain <domain>`, `--expiry <duration>` |
+| `create` | Create a temporary email address | `--domain <domain>`, `--expiry <duration>`, `--json` |
+| `list` | List all temporary emails | `--json` |
+| `wait` | Wait for incoming messages | `--email-id <id>`, `--timeout <seconds>`, `--json` |
+| `read` | Read email message content | `--email-id <id>`, `--message-id <id>`, `--json` |
+| `send` | Send email from temporary address | `--email-id <id>`, `--to <address>`, `--subject <text>`, `--body <text>`, `--json` |
+| `delete` | Delete temporary email | `--email-id <id>` |
+
+## Agent Workflow Example
+
+The CLI is designed to support agent-first automation. Here's a typical workflow:
+
+```bash
+# Create temporary email and extract details
+EMAIL=$(moemail create --domain moemail.app --expiry 1h --json)
+EMAIL_ID=$(echo $EMAIL | jq -r '.id')
+ADDRESS=$(echo $EMAIL | jq -r '.address')
+
+# Use ADDRESS for signup or service registration...
+
+# Wait for verification email
+MSG=$(moemail wait --email-id $EMAIL_ID --timeout 120 --json)
+MSG_ID=$(echo $MSG | jq -r '.messageId')
+
+# Read message content
+CONTENT=$(moemail read --email-id $EMAIL_ID --message-id $MSG_ID --json)
+
+# Extract verification code from CONTENT...
+
+# Cleanup
+moemail delete --email-id $EMAIL_ID
+```
+
+## JSON Output
+
+All commands support `--json` flag for structured output, making them ideal for agent automation:
+
+- **Success**: Command output in JSON format to stdout
+- **Errors**: Error messages written to stderr
+- **Exit Codes**:
+  - `0`: Command succeeded
+  - `1`: Runtime error (invalid input, service error)
+  - `2`: Configuration error (missing domain, invalid credentials)
+
+## Project Links
+
+- **Main Project**: https://github.com/beilunyang/moemail
+- **Issues & Feedback**: https://github.com/beilunyang/moemail/issues
+
+## License
+
+MIT