docs(agent): #76 require VM hibernate verify; LUKS+@swap reference

Agent must V2-test hibernation in the VM (encrypted BTRFS @swap
swapfile). Reference layout from live Latitude: no zram yet; swap
inside LUKS. MEMORY pointer for implementers.

agent/MEMORY.md

@@ -30,6 +30,12 @@ iteration would otherwise rediscover.
   realise it): extract the logic into a pure importable file and
   unit-test THAT (monitor-rules.nix / checks.display-profiles is the
   pattern).
+- **Hibernation reference (Latitude / Newton, BACKLOG #76):** LUKS whole
+  root BTRFS; `@swap` → `/swap`; file `/swap/swapfile`;
+  `boot.resumeDevice` = LUKS root UUID; `resume_offset` from
+  `btrfs inspect-internal map-swapfile -r`. Swap is encrypted with root
+  (not a cleartext partition). No zram on that box yet — zram is additive
+  for live pressure only. Installer already creates this when swapSize>0.
 - CI (`.gitea/workflows/check.yml`) is **eval-tier only** (standing
   decision 2026-07-10): act_runner docker-compose on the Gitea VPS; no
   KVM there. Full VM suite is BACKLOG **FUTURE #20**, not NEXT — needs a