contacts: extract into standalone skill, add himalaya wrapper for all email sends

Refactors the contacts system from being embedded in cal_tool.py into a
standalone contacts skill that serves as the single source of truth for
recipient validation across all outbound email paths.

- New skills/contacts/ skill: list, add, delete, resolve commands
- New skills/himalaya/scripts/himalaya.sh wrapper: validates To/Cc/Bcc
  recipients against contacts for message send, template send, and
  message write commands; passes everything else through unchanged
- cal_tool.py now delegates to contacts.py resolve instead of inline logic
- TOOLS.md updated: agent should use himalaya wrapper, not raw himalaya

skills/contacts/SKILL.md

@@ -0,0 +1,67 @@
+---
+name: contacts
+description: "Contact management with CardDAV sync. Validates email recipients for calendar invites and himalaya email sending. Prevents hallucinated addresses."
+metadata: {"clawdbot":{"emoji":"📇","requires":{"bins":["python3","vdirsyncer"]}}}
+---
+
+# Contacts
+
+Manage a local vCard contact list synced to Migadu CardDAV via vdirsyncer. Used by the calendar tool and himalaya wrapper to validate recipient addresses before sending.
+
+## Why This Exists
+
+LLMs can hallucinate email addresses — inventing plausible-looking addresses from context instead of looking up the correct one. This contact list serves as a **tool-level allowlist**: outbound emails can only go to addresses that exist in the contacts.
+
+**Adding contacts and sending emails are separate operations.** Never add a contact and send to it in the same request.
+
+## Prerequisites
+
+- Python 3 (no external dependencies)
+- `vdirsyncer` configured with a CardDAV pair for contacts sync
+- Contacts directory: `~/.openclaw/workspace/contacts/default/`
+
+## Usage
+
+```bash
+SKILL_DIR=~/.openclaw/workspace/skills/contacts
+
+# List all contacts
+$SKILL_DIR/scripts/contacts.sh list
+
+# Add a contact (single email)
+$SKILL_DIR/scripts/contacts.sh add --name "小鹿" --email "mail@luyx.org"
+
+# Add with email type and nickname
+$SKILL_DIR/scripts/contacts.sh add --name "小橘子" --email "Erica.Jiang@anderson.ucla.edu" --type work --nickname "小橘子"
+
+# Add a second email to an existing contact
+$SKILL_DIR/scripts/contacts.sh add --name "小橘子" --email "xueweijiang0313@gmail.com" --type home
+
+# Resolve a name to email address (used by other tools)
+$SKILL_DIR/scripts/contacts.sh resolve "小橘子:work"
+# Output: Erica.Jiang@anderson.ucla.edu
+
+# Delete a contact
+$SKILL_DIR/scripts/contacts.sh delete --name "小橘子"
+```
+
+## Resolve Formats
+
+The `resolve` command accepts three formats:
+
+| Format | Example | Behavior |
+|--------|---------|----------|
+| Name | `小橘子` | Match by FN or NICKNAME. Error if multiple emails (use type). |
+| Name:type | `小橘子:work` | Match by name, select email by type. |
+| Raw email | `user@example.com` | Accept only if the email exists in contacts. |
+
+Unknown addresses are **rejected** with the available contacts list shown.
+
+## Integration
+
+- **Calendar tool** (`cal_tool.py`): `send --to` calls `contacts.py resolve` before sending invites
+- **Himalaya wrapper** (`himalaya.sh`): validates To/Cc/Bcc headers before passing to himalaya for email delivery
+
+## Data
+
+Contacts are stored as vCard 3.0 `.vcf` files in `~/.openclaw/workspace/contacts/default/`, synced to Migadu CardDAV via vdirsyncer. Filenames are `{uid}.vcf`.