Clarify composites in part 2

After poking around to see how devs engage with BTs, I find that part 2 ideally should have a much cleaner structure where each status function (except terminals) is either a sequence or a selector.
The same applies to the example on *active-logic-cs*, one which is actually off-putting in that it is, well. Overly complex.
Aside - a galore showing small snippets demonstrating features; also a long overdue cheat-sheet/quick-ref section (file upstream)

No files are named, so first locate the Part 2 tutorial material and the `active-logic-cs` example in this repo’s docs. Review those sections to identify where status functions are described and simplify them into sequence/selector form except terminals. Then revise the example/structure and add short snippets plus a cheat-sheet/quick-ref section if present. Done means the referenced docs read with a cleaner flow and lower complexity.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.