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/himalaya/SKILL.md

@@ -9,6 +9,30 @@ metadata: {"clawdbot":{"emoji":"📧","requires":{"bins":["himalaya"]},"install"
 
 Himalaya is a CLI email client that lets you manage emails from the terminal using IMAP, SMTP, Notmuch, or Sendmail backends.
 
+## Recipient-Safe Wrapper
+
+Use the wrapper script (`scripts/himalaya.sh`) instead of calling `himalaya` directly. It validates outbound email recipients against the contacts list (see `skills/contacts/`) before sending.
+
+**Gated commands** (recipients validated before sending):
+- `message send` — parses To/Cc/Bcc from MIME headers on stdin
+- `template send` — parses To/Cc/Bcc from MML headers on stdin
+- `message write` — parses `-H` header flags for To/Cc/Bcc
+
+**Pass-through commands** (no validation needed):
+- Everything else: `envelope list`, `message read`, `message delete`, `folder`, `flag`, `attachment`, `account`, etc.
+
+```bash
+HIMALAYA=~/.openclaw/workspace/skills/himalaya/scripts/himalaya.sh
+
+# All commands work the same as `himalaya`
+$HIMALAYA envelope list
+$HIMALAYA message read 42
+
+# Sending commands validate recipients first
+cat message.txt | $HIMALAYA template send    # validates To/Cc/Bcc
+$HIMALAYA message write -H "To:小橘子:work" -H "Subject:Test" "body"
+```
+
 ## References
 
 - `references/configuration.md` (config file setup + IMAP/SMTP authentication)