Why is phenyl carbanion aromatic?
The lone pair of electrons will be in a $\mathrm{sp^2}$ hybridized orbital and not in  a pure p-orbital. Thus, it wil be in the same plane as the molecule. Only the lone pairs which are in an orbital perpendicular to the molecular plane can take part in resonance, so those $\mathrm{sp^2}$ electrons will not be counted in Hückel's rule.