Slight refactors in subcommand and search modules

[neunenak]

• adds some documentation comments for various methods on Search
• passes Compilation into several Subcommand handler methods to reduce cluttering up the outer scope of Subcommand::execute
• makes some code slightly more concise in a few areas

[casey]

I wasn't a huge fan of the refactor to init to use variables to store the justfile and working_directory, but otherwise looks good, made some tweaks to the docs, and passing in a Compilation is definitely an improvement.