The user spotted two white "beams" (20dp gaps) between the center
cell and the side cells. Root cause: the reference app's RelativeLayout
ignores the fixed 60dp width when a child has BOTH a left rule
(alignParentLeft) and a right rule (toLeftOf=center cell) - the width
is stretched to right-rule minus left-rule, i.e. 80dp on a 360dp
screen. The three cells therefore sit flush with only 2dp margins
between them, no gaps.
Port that behavior: side cells 60dp -> 80dp (6 places), center cell
stays 200dp centered. Verified against the reference screenshot pixel
measurements (side cells ~76.5dp incl. margins, center ~198dp).
Verified: feature + app compile, 11 unit tests pass. Marker lookup,
grid math and GPS logic untouched.