Fix Valgrind leaks in examples; use __jule_Str for conversions

[pgmtx]

I found memory leaks when running the examples under Valgrind: some error/early-return paths missed curl_slist_free_all and curl_easy_cleanup calls. This code fixes those leaks and removes the small strToString helper in favor of __jule_Str casts.

Notes:

• Behavior unchanged except proper cleanup.
• Small downside: more .get() calls in places.
• Tested with Valgrind; leak traces I saw are gone.