Kindle delivery

Use zlib kindle send for a local file. It uses SMTP and does not need a Z-Library login. If a book must be found or downloaded first, use the bundled zlib skill.

Send

Confirm zlib version succeeds and the requested file exists. If zlib is missing, install it as described in the zlib skill. Resolve an ambiguous file choice before sending. Reuse the user's existing choice.
If the user requested delivery and settings are already configured, run the command below without a TTY. Let the CLI resolve ZLIB_SMTP_PWD from its environment and .env files; checking only the shell variable is insufficient.
If settings are missing or the user requests setup, read SMTP setup, complete the missing settings, then send.