…ions

When a port of type std::vector<T> has a default empty value {} and no
input is specified in XML, toStr() converts the empty vector to "json:[]".
The explicit convertFromString specializations for vector types did not
handle the "json:" prefix (unlike the generic template), so this string
was split by ';' producing a vector with one literal "json:[]" element.

Fix: add "json:" prefix detection at the top of all four vector
convertFromString specializations (int, double, bool, string). When
detected, parse directly with nlohmann::json instead of splitting by ';'.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>