refactor(core): use MEDIUM_PROBE timeout for launchctl bootout/unload

Three call sites in lib/uninstall/batch.sh predated lib/core/timeouts.sh
and were still passing literal 5 to run_with_timeout. launchctl
bootout/unload is textbook MEDIUM_PROBE shape (a subprocess that
occasionally stalls under launchd contention, never a fast probe and
never a heavy disk walk). Wire them through MOLE_TIMEOUT_MEDIUM_PROBE_SEC
so future tuning lives in one place.

Also extend the 8s carve-out note in timeouts.sh to cover the deep
find /private/var/folders GPU-cache scan in lib/clean/system.sh, so the
"see lib/core/timeouts.sh" breadcrumb from that call site resolves to a
matching entry instead of leaving the next reader guessing.

After this change 14 literal run_with_timeout values remain, all of
which are documented carve-outs in the timeouts.sh header.