The default 128 MiB soft memory limit sits below the ~105 MB live heap the
full pexcn rule sets build, so the GC goal gets pinned to the live heap and
every allocation triggers a full-heap mark: measured 39% CPU on an otherwise
idle gateway with a GC cycle every 300-500 ms.
Raise the default to 512 MiB, resolve the limit in a testable helper that
covers GOMEMLIMIT/override/disable precedence, and declare the same value in
the packaged service plus the example configs so a deployment can tune it
without a rebuild.