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/kutil/kutil.k

@@ -14,6 +14,34 @@
   #  :python_cast (lambda s : __import__("kutil").parse_length("tex", s))
 @@@
 
+# Lengths on an axis (2026-09-16).  A width and a height are different
+# types so that a value can only name a unit of its own axis: "w" and "pw"
+# belong to widths, "h" and "ph" to heights, and a mistake is an argument
+# error rather than a silent misreading.  A BARE NUMBER is the natural
+# unit of the axis in every target -- characters for a width (a column in
+# txt, "ch" in html, the width of a digit in tex), lines for a height (a
+# newline in txt, "lh" in html, \baselineskip in tex) -- which is what lets
+# a klammer written for the page keep its meaning in a terminal.  "length"
+# stays for the quantities with no axis (a rule thickness).
+@@@argtype width |
+  a horizontal length.  A bare number is that many characters (one column
+  of plain text; in a proportional typeface, the width of a digit, so an
+  indent or a column lines up across lines even where the letters do not).
+  Otherwise a number with a unit: ^:width 2em, 12pt, 100px, .5w (that
+  fraction of the text width), .5pw (of the page width); f or none for an
+  element's natural width; a quoted string, whose set width is used where
+  the target can measure it.
+  :pattern 'float'^|'float'em^|'int'pt^|'int'px^|'float'w^|'float'pw^|f^|none^|"[^^"]+"
+@@@
+
+@@@argtype height |
+  a vertical length.  A bare number is that many lines (blank lines in
+  plain text; the line height of the surrounding text otherwise).
+  Otherwise a number with a unit: ^:height 2em, 12pt, 100px, .5h (that
+  fraction of the text height), .5ph (of the page height).
+  :pattern 'float'^|'float'em^|'int'pt^|'int'px^|'float'h^|'float'ph
+@@@
+
 @@@argtype lengths | a list of lengths
   :pattern ('length'^|\s+)*
   #:python_cast (lambda s : [__import__("kutil").parse_length("tex", e) for e in s.split()])
@@ -37,15 +65,18 @@
   An offset has no meaning for a centered element and is ignored there.
   Written alone, ^:offset is the standard indentation (e.g. ^:hpos left
   ^:offset), and a value overrides it (^:hpos right ^:offset 4em).
-  # A single-purpose type, not a use of "length", because the two values
+  # A single-purpose type, not a use of "width", because the two values
   # below are what the writer relies on and only a type can carry them: an
   # element is flush unless an offset is asked for (:default), and asking
   # without saying how much is the standard indentation (:alone).  A general
-  # length type must not declare :alone -- a bare option name has to read the
-  # same way wherever it appears, and "2em" is meaningless for :width.
-  :pattern 'length'
-  :default 0pt
-  :alone 2em
+  # width type must not declare :alone -- a bare option name has to read the
+  # same way wherever it appears, and "4" is meaningless for :width.
+  # Both values are BARE numbers -- characters -- so that they mean the same
+  # thing under txt as on the page (2026-09-16): four characters is about
+  # the 2em the alone value used to be, and 0 is flush everywhere.
+  :pattern 'width'
+  :default 0
+  :alone 4
 @@@