New `myclaude mail` group with:
- config: interactive account setup
- inbox: list recent messages
- read: show message by UID
- send: send email with attachments
- reply/forward: reply to or forward messages
Replace manual ctx.args parsing with a proper @click.option using
is_flag=False and flag_value='.'. This enables tab completion for
the --cwd / -C option and directory-only path completion after it.
Also bump click dependency to >=8.3.2 to avoid the optional-value
regression in 8.3.0/8.3.1.
--cwd was defined as a Click option but also parsed manually from ctx.args,
which caused conflicts when --cwd was followed by another flag (like
--dangerously-skip-permissions). Now --cwd is parsed entirely manually,
allowing:
--cwd alone -> use current directory
--cwd /path -> use specified path
(none) -> use myclaude project root (default)
Zhengshou Lai