keep gofmt composite-literal key alignment across Go 1.26/1.27

[exfly]

The piecewise-linear log2ish (2(f-1)) could push 41/geomean over 2.5 while math.Log/math.Exp stayed under it, splitting a column that Go 1.26 kept. Use the quadratic interpolant that still only needs Frexp/Ldexp/Floor.

closed: #81375

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