Provide lucky init --edge support

Nobody has claimed this yet.

One of the woes of installing lucky_cli from source is that, in order for `lucky init` to work properly, you must be on a tag.

I would be nice if the functionality of lucky init worked as such:

- `lucky init` always yields an app checked out from $LATEST_TAG of all respective repos
- If a user passes an `--edge` flag, `lucky init` uses `branch: main` for all lucky deps

We might be able to look to rails for how to achieve this.

One way this might work better too, is to have the "concerns" of app gen be inside lucky/another repo, and have the "lucky cli" functions in this repo, then clone via linked tag/edge from there.

Lots of ways to achieve this easily, but picking the best way for the future is important here.

Start at the `lucky init` command and trace how it selects versions and branches for Lucky dependencies. Compare the requested `$LATEST_TAG` behavior with `--edge` using `branch: main`, and review the Rails approach mentioned in the issue. Done means source installs generate apps from the latest tags by default and use main branches consistently when `--edge` is passed.

Written by the indexing model from the issue text.