I suggest to split the diff into two.
One for doing something with the signal list, if you decide to move it (or rather merge with the list in signal(3)).
And second for the .Tn removal etc (BTW why?). There is also .St macro, which might be appropriate in some places.

Beg me pardon please for the naive question.
What this revision basically does is changing the semantic of the pt_root. Instead being a real root of the trie, it becomes the starting point for search. The argument for not needed the real root is that we can always climb up to it from any node, following pn_parent. Am I right?

Why the man page added to libsys? It must go into libc/gen.

Deleted a few sentences that seemed redundant.
I think what now remains in the man page is useful
information.

To do what you're trying to do, you actually want to use the Makefile for this like I showed you in sched_getaffinity.3. As far as "is this the right approach", I am not familiar with the underlying topics to know.