txt section numbering, @typeface :middle/:lift and html scale, NewGardinerOmni, html :leading (from dev 9fa469dd74ed)

Section headings under txt are numbered inside a @document only; @typeface
gains :middle and :lift and its :scale now means the same in html and
pdf; NewGardinerOmni ships (OFL 1.1, Mark-Jan Nederhof) and @egyptian /
@chinese replace @cjk; @table :leading and :colsep reach html; kdesc
--typeface help names the flag; @document.txt is a Python class.

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

sks/target/phases.py

@@ -248,6 +248,50 @@ def txt_format_footnotes(text, K):
                        + label + " " + footnote + "\n\n")
     return result
 
+
+# Section numbering under txt (2026-09-18).  Numbering is a DOCUMENT
+# service, as it is in html (a pass @document runs over the page) and tex
+# (LaTeX's own counters inside the document): a heading rendered outside
+# a @document -- kdesc's renders of the ref/ generators -- is not
+# numbered.  Document.txt() (sks/document/document_txt.py) opens its
+# result with the document marker; Section.txt() emits a section marker
+# carrying the level and the :n override; this phase, first in the txt
+# and ansi lists, numbers the headings when the document marker is there
+# and strips every marker either way.  A heading at a level with no
+# parent numbers as "0.1", as html and tex print it -- the txt target
+# does not diverge from them.  The single-source functions are the
+# TODO #47 pattern.
+
+def txt_document_marker():
+    return "__KTEXTDOCUMENT__"
+
+def txt_section_marker(level, n=-1):
+    # LEVEL 0 is a part, 1-7 the sections; N > -1 sets the number.
+    return f"__KTEXTSECTION__{level}__{n}__"
+
+def txt_insert_section_numbers(text, K):
+    # The marker is the first thing the document emits, but the result
+    # reaches the phase behind whatever newlines the apply left in front.
+    head = text.lstrip()
+    in_document = head.startswith(txt_document_marker())
+    if in_document:
+        text = head[len(txt_document_marker()):].lstrip("\n")
+    levels = [0] * 8   # 0: parts; 1-7: sections (parts do not reset them, as in LaTeX)
+    marker_rgx = re.compile(r"__KTEXTSECTION__(\d+)__(-?\d+)__ ?")
+    def number(match):
+        if not in_document:
+            return ""
+        level, n = int(match.group(1)), int(match.group(2))
+        levels[level] = n if n > -1 else levels[level] + 1
+        if level == 0:
+            return f"{levels[0]} "      # a part resets nothing below it
+        for i in range(level + 1, len(levels)):
+            levels[i] = 0
+        return ".".join(str(v) for v in levels[1:level + 1]) + " "
+    return marker_rgx.sub(number, text)
+
+# HTML
+
 def html_footnote_marker():
     return "kt-footnote"