Users reported vol+ confirmation not registering on Magisk. The
prior backgrounded `getevent -qlc 1` + `kill -0` poll captured
the first kernel event of any type, then restarted on miss. With
six events per keypress (EV_MSC scan, EV_KEY DOWN, EV_SYN, then
release variants) and a 1s poll cadence, the 10s budget exhausts
before a DOWN sample lands. The chainfire note that piped getevent
breaks BusyBox grep applies under Magisk's ash standalone mode.
Replace with a single streaming `getevent -lq` matched inline
against `KEY_VOLUMEUP DOWN` / `KEY_VOLUMEDOWN DOWN`, wrapped in
`/system/bin/timeout 10`. Full paths bypass BusyBox aliasing.