v0.5.3

Fixed

• Duplicate environment keys now resolve to the last occurrence, matching what the guarded child
  observes. os/exec deduplicates its environment keeping the last entry, and HIPPO's own writer
  already produced that layout, but the reader returned the first match — so the guard could admit
  against one value while the process it launched read another. The trigger is ordinary:
  append(os.Environ(), "HIPPO_SESSION="+token) leaves a duplicate, and an ambient session from an
  outer guard shadowed the caller's explicit override, causing a spurious exit 75 instead of
  session inheritance. The same reader backs --concurrency-env mapping, the reservation clamp, and
  launcher identity detection.