iSpindle Plotter 0.5.22

A more robust original-gravity estimate. Original gravity is read from the settled plateau at the very start of the ferment. That level now uses the median of those readings rather than the mean, so it shrugs off an early krausen / CO2 spike inside the window no matter how large — OG stays anchored to the true settled value rather than being nudged up by the rise. On a clean start the two agree; the median just holds up better when the start is messy.