Improve the tutorial using Diataxis as a guideline: https://diataxis.fr/tutorials/

The current tutorial is quite good, but it could make use of some improvements. The first that comes to mind, is:

• Provide a clear picture before we start the tutorial
• Some parts of the tutorial could make use clearer steps.
  • gh-95271: Extract placeholders howto from sqlite3 tutorial #95522
• Make the wording more to the point; avoid options and alternatives.
• Offer only minimum necessary explanation

Suggesting to split this up into multiple PRs, for the reviewers convenience.