feat(cli): add upgrade alias and register mail command

- Add upgrade as an alias for update
- Register mail_cmd in CLI entrypoint

myclaude/cli.py

@@ -4,7 +4,7 @@ from importlib.metadata import PackageNotFoundError, version
 
 import click
 
-from myclaude.commands import chat_cmd, update_cmd
+from myclaude.commands import chat_cmd, mail_cmd, update_cmd, upgrade_cmd
 
 
 def _package_version() -> str:
@@ -21,7 +21,9 @@ def cli() -> None:
 
 
 cli.add_command(update_cmd)
+cli.add_command(upgrade_cmd, name="upgrade")
 cli.add_command(chat_cmd)
+cli.add_command(mail_cmd)
 
 
 def main() -> None:

myclaude/commands/__init__.py

@@ -1,6 +1,10 @@
 """CLI subcommands."""
 
 from .chat import chat_cmd
+from .mail import mail_cmd
 from .update import update_cmd
 
-__all__ = ["chat_cmd", "update_cmd"]
+# alias: upgrade is the same as update
+upgrade_cmd = update_cmd
+
+__all__ = ["chat_cmd", "mail_cmd", "update_cmd", "upgrade_cmd"]