tmux-plugins/tpm ? reverse-engineered prompt

Build me a simple tmux plugin manager that I can drop into my tmux setup and use to install, load, update, and remove plugins from my tmux config.

I want it to read a list of plugins from my tmux.conf, clone them into a local plugins folder, source them when tmux starts, and give me easy key bindings to install new plugins, update everything, and uninstall ones I removed from the config. It should work with tmux on Linux, macOS, and Cygwin, and only depend on common tools like bash and git.

Please include clear setup instructions, a small help guide for common issues, and enough tests or checks so I can trust it works. If you need to look up current tmux plugin behavior or config details online, go ahead and do that.