v0.8.0

v0.8.0: smoother wheel accel — slow-speed floor + speed-gated notches

Two new [wheel] knobs, tuned into the mac-like default (min_multiplier
0.9, steps_above 1.5):

- min_multiplier: multiplier floor at slow speed. Below 1.0 it de-amplifies
  slow scrolling for finer control in magnitude apps (Chrome/Firefox).
- steps_above: only emit discrete notches once the multiplier passes this.
  Below it a single fine hi-res event keeps smooth apps gliding; above it,
  notches so fixed-step apps (Flutter/Electron, e.g. Ubuntu App Center)
  still accelerate on fast flicks.

Wired through the daemon curve, config parse/validate/print, and the live
tune UI (two new rows on the Wheel tab). Defaults for the other presets are
neutral (1.0/1.0), reproducing the prior curve.