Analyze a file format of a song.

## Spec

File: ./Test.pro (file ext are always .pro)

- every song contains parts (name group here) (here: Verse 1, Verse 2, Chorus, ...) but could be any name
- every group contains 1-x slides
- every song contains different arrangements (here normal and test2) that defines the existence and the order of the groups
- every slide CAN have another textbox which contains a translated version of the first textbox

## ToDo

1. analyse the file structure and find all of the described specs.
2. test and verify if the definition is correct - there is a `all-songs` directory with lot of examples.
3. describe the structure for future AI prompts to use these files in `spec/pp_song_spec.md` and describe the usage in the `AGENTS.md` (replace obsolet commands)
4. write a PHP module (is later used in laravel) in `./php` which can parse a song and let get/set every aspect of structure. Use Objects here (Song, Group, Slide, Arrangement, etc)
5. create a simple PHP cli tool, which receive a param with a song file and show the structure of the song.