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>

mac/file.h

@@ -55,6 +55,7 @@ fs::path klammertext_filename(
     const std::string& basename, bool error_if_missing=true, bool make_directory_if_missing=false);
 std::vector<std::string> sks_dirs();
 std::vector<std::string> get_sks_directories(const std::string& s, bool include_argument=true);
+std::string symbolic_klammertext_filename(std::string filename);
 std::string cache_directory(const std::string& subdirectory, std::string parent_directory="");
 std::time_t to_time_t(const fs::file_time_type& ftime);
 bool in_modification_order(std::string filename1, std::string filename2);