docs: define QNAP watchdog singleton contract (#1617)

docs/release-control/v6/internal/subsystems/agent-lifecycle.md

@@ -5108,7 +5108,12 @@ check when both paths share a filesystem, honors an operator-selected
 Unraid watchdogs must route agent output through the agent's rotating
 `--log-file` writer instead of an unbounded shell append; their own watchdog
 messages must also be size-bounded so either logging path cannot exhaust a
-RAM-backed appliance root.
+RAM-backed appliance root. The QNAP wrapper is also a singleton lifecycle
+owner: concurrent starts from flash-backed `autorun.sh` and an install or
+upgrade must elect exactly one watchdog before terminating or launching an
+agent. The elected watchdog records both supervisor and child PIDs, removes
+only lock state it owns, and terminates its child on shutdown so a second
+watchdog or orphan agent cannot accumulate appliance CPU.
 
 Unified Agent lifecycle truth is agent-authored. The host report contract now
 carries the non-secret applied managed-config fingerprint, self-updater state

docs/release-control/v6/internal/subsystems/deployment-installability.md

@@ -2750,7 +2750,13 @@ an operator-supplied `TMPDIR`. `--preflight-only` must exercise the same
 storage check and report an actionable alternate-temporary-directory hint.
 Generated QNAP and Unraid watchdogs must use the agent's rotating `--log-file`
 path rather than an unbounded stdout append, while keeping watchdog-owned
-messages independently size-bounded.
+messages independently size-bounded. Because QNAP may launch the same
+persistent wrapper from both flash-backed `autorun.sh` and an installer or
+upgrader, that wrapper must acquire one portable atomic singleton lock before
+killing or starting an agent, track its owned child, recover stale lock state,
+and remove only its own PID and lock artifacts on shutdown. Installer
+verification must exercise concurrent wrapper launches and prove that they
+produce one watchdog/agent pair with no orphan after termination.
 
 The in-app updater's apply pipeline now owns a downgrade guard on the normal
 apply path. A syntactically valid release asset URL can name a release older