escapeIri

Escapes iri for safe emission inside <...> angle brackets in N-Triples / Turtle / N3. The IRIREF production forbids control characters (U+0000–U+0020) and < > " { } | ^ \` unescaped; we replace each with a \\uXXXX UCHAR so a hostile or merely unusual IRI can't break out of the term and corrupt the serialized document. Returns the input unchanged when it contains none of those characters.