Width and height argtypes, kdesc --argtypes from ref/, txt @define/@left_right/@columns, kdiag --check value validation (from dev d6993110e9b3)

Also: the klammertext argtype (descriptions kept as source), txt table
wrapping and :hpos/:offset, @c between ‹ ›, txt section headings, the
ktext newline-only trim, capitalize(), and the argtype test suite.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -51,7 +51,7 @@ are regenerated on each release — patches cannot be merged directly.
 Report problems (or send patches) to the author; accepted changes are
 applied to the development tree and appear in a following snapshot.
 
-This snapshot was assembled from development commit `fcec5e2e77ac`.
+This snapshot was assembled from development commit `d6993110e9b3`.
 
 ## License