How it all works, seen as a whole

What this part is for. Before any of the six parts that follow go deep on one piece, this part gives the whole shape once, cleanly, so nothing later has to be explained from nowhere. It answers the question a genuinely new reader actually has — "if I had never seen this system before, what is the one picture I should carry into everything else?"

The one-sentence version: everything the system knows is one append-only list of small records; every visible behaviour — a form appearing, a question being answered, a report being written — is a small piece of code that watches that list for something specific and, once it sees it, adds more to the list.