mcurl

Expand API: setopt/getinfo, auth, cookies, redirects, encoding, dup, pause, callbacks, context managers, convenience getters

Performance: use sets for socket tracking, deque for tunnel data, optimize yield_msgs

Remove old libcurl version checks, build workflow only on main push

Update to libcurl 8.19.0, native ARM CI, expanded Windows matrix

Merge devel into main: modernize mcurl with CI/CD, tests, docs, wheels