By Kirchoff laws, same current flows through all cells in series. If you cut the path anywhere, no current can flow. As a consequence, current measurement and overcurrent (including short circuit) protection is done once, on the pack level.
Possibility of current taking alternative routes is prevented by good mechanical design.
If you try to come up with a design where each series element is separately protected "for modularity", the cost and complexity will blow through all roofs. Such protection needs to handle the full pack voltage, after all, so single-cell integrated solutions won't work. Just don't do it.