Clean up returned embeds and messages

Right now responses to commands don't really have a lot of thought put into them so it would be nice to get them cleaned up, some sense of uniformity and deciding what gets displayed to the end user and in what ways

Start by locating the bot command handlers where replies are built and list all returned embeds/messages across commands. Compare current formatting and decide a single presentation pattern (embed fields, wording, error/info tone) to apply consistently. First run the bot and exercise core music commands to see current output, then implement the cleanup in those response paths and verify results. Mark the issue done when user-facing outputs are consistent across commands and no unintended message content is shown.

索引モデルが issue の本文から書いたものです。