Production quality monitor (sampling planner + per-segment alert)

A dependency-free (pure standard-library) Python tool for the AFTER-LAUNCH monitoring operation this article describes — distinct from the pre-launch gate (5.5) and regression suite (5.6). It does NOT decode video or compute VMAF/P.1203 itself; it consumes records you have already measured (a no-reference/bitstream score, or a player 'below-target' flag) and runs the two pieces of math the article centers on. (1) SAMPLING PLAN: sizes a representative sample from the margin of error you want, mar