* test: keep mini-allocated ports below the ephemeral floor
Allocated ports could land in 32768-55000, so a transient outbound dial
during mini startup (volume->master gRPC, etc.) could grab an allocated
port as its source port before the filer bound it, failing with
"bind: address already in use". Cap the range so port+GrpcPortOffset
stays under 32768.
* test: derive mini port cap from the ephemeral floor constant
Name the 32768 floor once and compute miniPortMax as floor-GrpcPortOffset
so the cap tracks the offset; reuse the constant in the regression test.