Escaping, table layout, and document fixes

Quoted Klammertext specials (^@ ^| ^# ^^ ^: ^*) and ^'...'^ regions now
survive re-processing (held as escape markers until final output);
:after_apply phase functions receive and return raw target text.

Tables: :hpos element position (center|left|right|<length>) replaces the
unimplemented :center/:indent; the ranged cell override is renamed
:justify; :column_width works in html (colgroup widths) and gains
'fill' -- the remaining width, capped at the column's widest entry, in
both targets; a table wider than the text column warns on the console;
table edges without an outer line set their text flush on the margins.

@document: no empty title bar for untitled documents; @vfill fills to
the bottom of the window in html (pure CSS); @vspace in plain text;
new @dot klammer; monospace email links.

mac/target.h

@@ -47,3 +47,16 @@ public:
 
 std::vector<std::pair<std::string, std::string>>
 parse_transforms(std::string transform_string);
+
+// Decode every KTESC<hex>KTESC marker in text back to its original
+// characters.  Used for the final output (after target-declared escapes have
+// been resolved to their replacements) and for programmatic use of argument
+// values.  The Python counterpart is unescape_ktesc() in klammer_base.py.
+std::string ktesc_resolve(std::string text);
+
+// Replace each Klammertext structural character (@ | # ^ : *) in s with its
+// KTESC marker, so text that has already been interpreted once (quoted
+// specials, ^'...'^ literal content) survives re-katomization by
+// sub-Machines and the @eval result read-back.  Resolved by ktesc_resolve()
+// at final processing.
+std::string hide_structural_characters(const std::string& s);