对于平面直角坐标系\(xOy\)中的点\(P\)和\(⊙C\),给出如下定义:如果\(⊙C\)的半径为\(r\),\(⊙C\)外一点\(P\)到\(⊙C\)的切线长小于或等于\(2r\),那么点\(P\)叫做\(⊙C\)的“离心点”.
\((1)\)当\(⊙O\)的半径为\(1\)时, \(①\)在点\(P\)\({\,\!}_{1}\)\((\)\(\dfrac{1}{2}\),\(\dfrac{\sqrt{3}}{2}\)\()\),\(P\)\({\,\!}_{2}\)\((0,-2)\),\(P\)\({\,\!}_{3}\)\((\)\(\sqrt{5}\),\(0)\)中,\(⊙O\)的“离心点”是____;
\(②\)点\(P(m,n)\)在直线\(y=-x+3\)上,且点\(P\)是\(⊙O\)的“离心点”,求点\(P\)横坐标\(m\)的取值范围;
\((2)⊙C\)的圆心\(C\)在\(y\)轴上,半径为\(2\),直线\(y=-\dfrac{1}{2}x+1\)与\(x\)轴、\(y\)轴分别交于点\(A\),\(B.\) 如果线段\(AB\)上的所有点都是\(⊙C\)的“离心点”,请直接写出圆心\(C\)纵坐标的取值范围.