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/block/block.k

@@ -31,10 +31,10 @@ vertical mode is a no-op.
 
 # Indented block
 
-@@indent.k s :left.int 8 :right.int -1 :ragged.bool false :
-Indented block. The *left* and *right* values are the number of characters for
-indentation (as roughtly defined by "ex"). By default, *right* is set to the
-*left* value (with -1 as the sentinel).
+@@indent.k s :left.width 8 :right.width :ragged.bool false :
+Indented block. *left* and *right* are widths: a bare number is that many
+characters (the width of a digit in a proportional typeface), or a width
+with a unit such as 2em. *right* defaults to the *left* value.
 @@
 @@indent.html,tex,txt :: @eval block.Indent(K) eval@ @@
 
@@ -124,13 +124,12 @@ indentation (as roughtly defined by "ex"). By default, *right* is set to the
 @@extendpage.tex :: \enlargethispage{*linecount*\baselineskip} @@
 @@extendpage.txt :: @@
 
-
 # Vertical space
 
-@@vspace.k lines.float : Vertical space, in multiples of the current line height @@
-@@vspace.tex :: \vspace{*lines*\baselineskip} @@
-@@vspace.html :: <div style="height: *lines*lh"></div> @@
-@@vspace.txt :: @eval phases.txt_vspace_marker() * round(*lines*) @ @@
+# The first parameter of the height type: a bare number is lines in every
+# target (as it always was here), and a unit may now be given.
+@@vspace.k lines.height : Vertical space: a number of lines, or a height such as 2em @@
+@@vspace.html,tex,txt :: @eval block.Vspace(K) @ @@
 
 # Vertical fill to end of page
 
@@ -146,6 +145,10 @@ only makes some vertical space. @@
 @@vfill.html :: <div class="vfill"></div> @@
 @@vfill.txt :: @vspace 3 @ @@
 
+# Horizontal space
+@@hspace.k width.width : Horizontal space of the given *width* (a bare number is characters) @@
+@@hspace.html,tex,txt :: @eval block.Hspace(K) @ @@
+
 
 # Questions and answers
 
@@ -202,7 +205,7 @@ bar (|) between each line. Then, two bars (||), and the right lines with a bar
 betwen them.
 @@
 
-@@left_right.html,tex :: @eval block.Left_right(K) @ @@
+@@left_right.html,tex,txt :: @eval block.Left_right(K) @ @@
 
 
 # Footnote