.已知\(x\)\(∈R\),使得关于\(x\)的不等式\(|x-\)\(1\)\(|-|x-\)\(2\)\(|\)\(\geqslant \)\(t\)恒成立.
\((1)\)求满足条件的实数\(t\)所构成的集合\(T\)\(;\)
\((2)\)若\(m > \)\(1\),\(n > \)\(1\),且对于\(∀\)\(t\)\(∈\)\(T\),不等式\(\log _{3}\)\(m\)\(·\log _{3}\)\(n\)\(\geqslant \)\(t\)恒成立,试求\(m+n\)的最小值.