fix(server): t3 service install no longer moves a --base-dir service onto an empty ~/.t3#23878

refactor(server): trim the base-dir fix to the install guard

fix(server): restart and maintenance pauses treat a symlinked home as this one

test(server): cover install with an unreadable service unit

fix(server): fail closed on unreadable units and accept symlinked homes

fix(server): t3 service install no longer rebinds another home's service