alwaysShow property

Force the bracket ON, overriding the automatic Behind Bars rule.

show is the force-OFF half of the pair and always was; this is the force-ON half, and it did not exist before 2.7.2 because it had nothing to override — shouldShow had no production caller, so every tuplet was bracketed unconditionally by TupletRenderer and "force on" was simply what happened. Now that the renderer asks the rule, an author who wants a bracket over a beamed group anyway (a common editorial choice in pedagogical and orchestral parts, where the group is easier to read bracketed) needs a way to say so on the STEM side. BracketSide.notehead also forces the bracket, but it means "vocal music, bracket by the noteheads" and moves the bracket; this does not move anything.

show = false still wins over this: an explicit "never" beats an explicit "always", because suppression is the narrower request.