feat: add himalaya email CLI skill

Add skill for Himalaya (https://github.com/pimalaya/himalaya), a CLI
email client supporting IMAP, SMTP, Notmuch, and Sendmail backends.

Includes:
- SKILL.md with common operations (list, read, reply, forward, send)
- Configuration reference for Gmail, iCloud, and generic IMAP/SMTP
- MML (MIME Meta Language) composition guide for attachments

Tested with iCloud IMAP account - verified folder listing, email
reading, and sending work correctly.

skills/himalaya/SKILL.md

@@ -0,0 +1,225 @@
+---
+name: himalaya
+description: "CLI to manage emails via IMAP/SMTP. Use `himalaya` to list, read, write, reply, forward, search, and organize emails from the terminal. Supports multiple accounts and message composition with MML (MIME Meta Language)."
+homepage: https://github.com/pimalaya/himalaya
+metadata: {"clawdbot":{"emoji":"📧","requires":{"bins":["himalaya"]},"install":[{"id":"brew","kind":"brew","formula":"himalaya","bins":["himalaya"],"label":"Install Himalaya (brew)"},{"id":"cargo","kind":"shell","cmd":"cargo install himalaya","bins":["himalaya"],"label":"Install Himalaya (cargo)"}]}}
+---
+
+# Himalaya Email CLI
+
+Himalaya is a CLI email client that lets you manage emails from the terminal using IMAP, SMTP, Notmuch, or Sendmail backends.
+
+## References
+
+- `references/configuration.md` (config file setup + IMAP/SMTP authentication)
+- `references/message-composition.md` (MML syntax for composing emails)
+
+## Prerequisites
+
+1. Himalaya CLI installed (`himalaya --version` to verify)
+2. A configuration file at `~/.config/himalaya/config.toml`
+3. IMAP/SMTP credentials configured (password stored securely)
+
+## Configuration Setup
+
+Run the interactive wizard to set up an account:
+```bash
+himalaya account configure
+```
+
+Or create `~/.config/himalaya/config.toml` manually:
+```toml
+[accounts.personal]
+email = "you@example.com"
+display-name = "Your Name"
+default = true
+
+backend.type = "imap"
+backend.host = "imap.example.com"
+backend.port = 993
+backend.encryption.type = "tls"
+backend.login = "you@example.com"
+backend.auth.type = "password"
+backend.auth.cmd = "pass show email/imap"  # or use keyring
+
+message.send.backend.type = "smtp"
+message.send.backend.host = "smtp.example.com"
+message.send.backend.port = 587
+message.send.backend.encryption.type = "start-tls"
+message.send.backend.login = "you@example.com"
+message.send.backend.auth.type = "password"
+message.send.backend.auth.cmd = "pass show email/smtp"
+```
+
+## Common Operations
+
+### List Folders
+
+```bash
+himalaya folder list
+```
+
+### List Emails
+
+List emails in INBOX (default):
+```bash
+himalaya envelope list
+```
+
+List emails in a specific folder:
+```bash
+himalaya envelope list --folder "Sent"
+```
+
+List with pagination:
+```bash
+himalaya envelope list --page 1 --page-size 20
+```
+
+### Search Emails
+
+```bash
+himalaya envelope list --query "from:john@example.com subject:meeting"
+```
+
+### Read an Email
+
+Read email by ID (shows plain text):
+```bash
+himalaya message read 42
+```
+
+Read as raw MIME:
+```bash
+himalaya message read 42 --raw
+```
+
+### Reply to an Email
+
+Interactive reply (opens $EDITOR):
+```bash
+himalaya message reply 42
+```
+
+Reply-all:
+```bash
+himalaya message reply 42 --all
+```
+
+### Forward an Email
+
+```bash
+himalaya message forward 42
+```
+
+### Write a New Email
+
+Interactive compose (opens $EDITOR):
+```bash
+himalaya message write
+```
+
+Send directly using template:
+```bash
+cat << 'EOF' | himalaya template send
+From: you@example.com
+To: recipient@example.com
+Subject: Test Message
+
+Hello from Himalaya!
+EOF
+```
+
+Or with headers flag:
+```bash
+himalaya message write -H "To:recipient@example.com" -H "Subject:Test" "Message body here"
+```
+
+### Move/Copy Emails
+
+Move to folder:
+```bash
+himalaya message move 42 "Archive"
+```
+
+Copy to folder:
+```bash
+himalaya message copy 42 "Important"
+```
+
+### Delete an Email
+
+```bash
+himalaya message delete 42
+```
+
+### Manage Flags
+
+Add flag:
+```bash
+himalaya flag add 42 --flag seen
+```
+
+Remove flag:
+```bash
+himalaya flag remove 42 --flag seen
+```
+
+## Multiple Accounts
+
+List accounts:
+```bash
+himalaya account list
+```
+
+Use a specific account:
+```bash
+himalaya --account work envelope list
+```
+
+## Attachments
+
+Save attachments from a message:
+```bash
+himalaya attachment download 42
+```
+
+Save to specific directory:
+```bash
+himalaya attachment download 42 --dir ~/Downloads
+```
+
+## Output Formats
+
+Most commands support `--output` for structured output:
+```bash
+himalaya envelope list --output json
+himalaya envelope list --output plain
+```
+
+## Sync Mode
+
+For faster access, enable local caching:
+```bash
+himalaya account sync personal
+```
+
+## Debugging
+
+Enable debug logging:
+```bash
+RUST_LOG=debug himalaya envelope list
+```
+
+Full trace with backtrace:
+```bash
+RUST_LOG=trace RUST_BACKTRACE=1 himalaya envelope list
+```
+
+## Tips
+
+- Use `himalaya --help` or `himalaya <command> --help` for detailed usage.
+- Message IDs are relative to the current folder; re-list after folder changes.
+- For composing rich emails with attachments, use MML syntax (see `references/message-composition.md`).
+- Store passwords securely using `pass`, system keyring, or a command that outputs the password.
+