Wires the reset-on-change behaviour onto a CngxPaginate brain: when
key() changes (after the initial run) the paginator jumps to the first
page. The first run captures the mounting value without resetting, and an
already-first paginator emits nothing.
Shared by [cngxPaginateResetOn], the CngxPaginator shell's resetOn
input, and the CngxMatPaginator bridge's resetOn input, so the behaviour
is byte-identical across all three. Call inside an injection context
(constructor or field initialiser).