Make the run to the net and back a double tap

Oliver: "das Vorlaufen und Zurücklaufen sollte durch einen Doppeltipp
ausgelöst werden". It replaces v374's flick-length rule: the long
up-flick is only the deep ball again, the long down-flick only the lob.

While his own ball flies there is nothing to hit, so a tap there is not
a swing. Two inside 0.35 s take him in to the net from the back, or back
from the net. "TO THE NET" or "BACK" pops under him. An incoming ball
keeps every tap a swing, so the two meanings never share a moment. After
his own serve it is serve and volley. The short-ball approach stays
automatic.

Measured: the base ladder is unchanged, and following the ball in still
pays against pushers and costs against big hitters. Three tests replace
v374's two; v376.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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