Verbatim-safe typography, ^-punctuation quoting, full-range ^UUUU^, polyglot html

Typographic transforms (---, quote pairs, ~) no longer touch verbatim
text: @c/@code/@source_listing content and ^'...'^ spans show exactly the
characters written. "^" before any punctuation character quotes it in
every target (the apostrophe excepted: ^' opens a literal span), with the
new :resolve option on @@@target declaring per-target renderings. The
^UUUU^ code-point form accepts 4-6 hex digits, the full Unicode range.
The html output and transform spellings are polyglot (XML-valid), in
preparation for an EPUB target. New suites: transform_test, character_test
(engine), typography_test (SKS).

(from dev 07ce5ea86a0a)

tst/editor/indent_literal_c.kt

@@ -0,0 +1,11 @@
+@document :text
+  @i before @c @right c@ after @ @x@
+    @note
+  inside the note
+    @
+  @c content with basic@ inside c@ and after
+  @c
+     kept   as-is # not a comment
+  c@
+  after everything
+@

tst/editor/indent_literal_c_expected.kt

@@ -0,0 +1,11 @@
+@document :text
+@i before @c @right c@ after @ @x@
+@note
+  inside the note
+@
+@c content with basic@ inside c@ and after
+@c
+     kept   as-is # not a comment
+  c@
+after everything
+@

tst/editor/vim_feature_test.vim

@@ -81,6 +81,22 @@ call s:Check('abbreviated @name-',  s:Syn(9, 1) ==# 'klammertextAppOpen'
       \ && s:Syn(9, 6) ==# '' && s:Syn(9, 7) ==# '', s:Syn(9, 6))
 call s:Check('file marker ##',     s:Syn(10, 1) ==# 'klammertextMarker',   s:Syn(10, 1))
 call s:Check('## removes to EOF',  s:Syn(11, 3) ==# 'klammertextRemovedFile', s:Syn(11, 3))
+
+" @c is the single-letter literal klammer (inline @code, 2026-08-16).  A
+" fresh buffer: the ## in the buffer above removes to EOF.  The traps a
+" single-letter name adds: a word ending in c ("basic@") must not close the
+" region, and "@caption" must not open one.
+enew!
+call setline(1, [
+      \ '@c y @ basic@ z c@ tail',
+      \ '@caption arg @'])
+set filetype=klammertext
+call s:Check('c verbatim open @c',   s:Syn(1, 1)  ==# 'klammertextAppOpen',  s:Syn(1, 1))
+call s:Check('c interior @ verbatim', s:Syn(1, 6)  ==# 'klammertextVerbatim', s:Syn(1, 6))
+call s:Check('basic@ does not close @c', s:Syn(1, 13) ==# 'klammertextVerbatim', s:Syn(1, 13))
+call s:Check('real close c@',        s:Syn(1, 17) ==# 'klammertextAppClose', s:Syn(1, 17))
+call s:Check('text after c@ plain',  s:Syn(1, 20) ==# '',                    s:Syn(1, 20))
+call s:Check('@caption opens @caption, not @c', s:Syn(2, 1) ==# 'klammertextAppOpen', s:Syn(2, 1))
 else
   call add(s:results, 'SKIP syntax checks (this Vim lacks +syntax)')
 endif