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/katom.cpp

@@ -140,6 +140,18 @@ std::string as_string(const katom_list& ks, bool strip_whitespace)
     return as_string(ks.begin(), ks.end(), strip_whitespace);
 }
 
+std::string as_source(std::vector<Katom>::const_iterator begin, std::vector<Katom>::const_iterator end, bool strip_whitespace)
+{
+    std::string result {};
+    for (auto ki = begin; ki < end; ki++) {
+        if (ki->m_type != katom_t::replaced && ki->m_type != katom_t::ignored)
+            result += ki->m_src;
+    }
+    if (strip_whitespace)
+        result = trim(result);
+    return result;
+}
+
 katom_list trim(katom_list& katoms, std::set<katom_t> trim_types)
 {
     katom_iter begin =