Use filenames as code block labels instead of <shell>, <python>

[florence-bockting]

Description

In the Local Rule Execution section, localrules is introduced but it is not clear in which file it should be placed (i.e., the Snakefile).

More broadly, code blocks throughout the lesson use generic language tags (e.g. python, shell) rather than indicating the target file, which makes it harder for learners to know where to apply changes.

Suggested improvements

• Explicitly state that localrules belongs in the Snakefile and show the complete file contents at that point in the lesson, so learners always have a clear reference state.
• Replace generic code block labels (e.g. python, shell) with the actual filename (e.g. Snakefile, cluster_profile/config.yaml) to make it immediately clear where each code snippet belongs.