The reader test doubles skipped every line that actually opens a file: with
resolveCgroupV2MemoryDir, readLinuxCgroupMemoryLimitFromSysfs and
readLinuxMemoryPressureStallFromProcfs each throwing on entry, all 306
crash-reporting tests still passed. Adds a pseudo-file seam (shared by both
modules, as the single reader already was) and tests the namespace mount-root
fallback, the root-cgroup rejection, the all-undefined silence and PSI's
absence.
pre-gone-host-memory.test.ts calls getSystemMemoryDetails('linux') with the real
readers live, so on a memory-capped or busy Linux runner its label assertion
reads the runner's own cgroup and fails; seams it like the new files do.
Corrects the doc's blanket "an absent row means could not measure": memory.max
reading `max` is also reported as an absent field, and CgroupCurrentMB is what
separates the two.
Claude
38e40f3618