fix: do not treat -m substring in %run paths as module option 🤖🤖 - #15400

fix: do not treat -m substring in %run paths as module option 🤖🤖

%run inserted -- after -m whenever the option string contained the substring -m. A script path like test-main.py matched that check, shlex.join rewrote the line, and the file did not run.

Only rewrite when -m is an exact argv token.

Fixes #14849