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/document/document_txt.py

@@ -0,0 +1,33 @@
+import kutil
+import klammer_base
+import phases
+
+class Document(klammer_base.Klammer_base):
+    def __init__(self, K):
+        super().__init__(K)
+        if self.files:
+            raise Exception("The :files option is not defined for the 'txt' target")
+
+    def html(self):
+        raise Exception("Implemented by document.cpp")
+
+    def tex(self):
+        raise Exception("Implemented by document.cpp")
+
+    def txt(self):
+        # The document marker: section numbering under txt is a document
+        # service, and the numbering phase numbers only when it finds this
+        # at the head of the text (a fragment, as kdesc renders, has none).
+        result = phases.txt_document_marker() + "\n"
+        if self.title:
+            result += f"@b {self.title} @ @nl@\n"
+            if self.subtitle:
+                result += f"@b {self.subtitle} @ @nl@\n"
+            result += "\n"
+        if self.author:
+            result += f"@i {self.author} @ @nl@\n"
+        if self.date:
+            result += f"@i {self.date} @ @nl@\n"
+        result += "\n"
+        result += self.text
+        return result