How do I calculate the power rating for zero-ohm resistors?
Yageo specifies both maximum current and maximum power, see page 5 of the datasheet:


  \$P_{max}\$: 100 mW
  \$I_{max}\$: 1 A  


and you'll also see that for the jumper


  \$R_{max}\$: 50 m&Omega;  


That seems inconsistent: 1 A through 50 m&Omega; is only 50 mW, not 100 mW. In these cases you have to work with the lower value: 50 mW, since 100 mW would mean a 1.4 A current, which exceeds the 1 A limit.

EEs often scoff at the 5 % tolerance specification for the 0 &Omega; resistor. The engineers at Yageo know that that doesn't make sense, and if you take a good look at page 2 you'll see that they don't specify 5 % for the jumper at all:


  F = ± 1 %
  J = ± 5 % (for Jumper ordering, use code of J)  


which should be read as "we use the same code for a jumper as the tolerance for other values". It does not implied that the 5 % tolerance would apply to the jumper.

Specifying maximum power isn't silly either: the part's weight and specific thermal capacity determine that, regardless of resistance value.