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>

sks/code/code.k

@@ -24,7 +24,7 @@ string, so a "^#" or a bare "^@" inside it was read as Klammertext and usually
 failed the file, which is not what "verbatim" can mean.
 @@
 
-@@c.html,tex :: @eval code_block.Code_fragment(K) eval@
+@@c.html,tex,txt :: @eval code_block.Code_fragment(K) eval@
 @@
 
 # :cwd makes the filename resolve against the DOCUMENT's directory, not