LM331 nominal charge/window experiment

Host: python lm331_window.py --vin 1 --window 0.1
User-entered count: python lm331_window.py --vin 1 --window 0.1 --count 98
Tests: python -B test_lm331.py
No external Python dependencies. Code is host-only; no MCU required.
Physical fixture is an unmeasured TI LM331N/NOPB source-based design,5V/0.2..2V.
Model excludes real47ohm branch, offsets, source compliance/startup and capacitor parasitics.
Blank CSV is not a measured log. Do not infer hardware/target verification from host tests.
