Owns the node-local :erlang.system_monitor/2 subscription and tracks whether a local-pause event is currently suppressing φ-computation confidence.

Subscribes to three conditions:

• {:long_schedule, N} — a process held a scheduler for > N ms
• {:long_gc, N} — GC took > N ms
• :busy_dist_port — the distribution TCP send buffer filled; heartbeats are queued behind user traffic. This is the head-of-line blocking signal and is the primary reason v1 is observability-grade rather than decision-grade.

When any of these fire, pause state flips to true for a lockout window (default 500 ms). Each new event extends the window. State is published via :persistent_term so estimators can read it without synchronising on this GenServer.

Telemetry:

• [:phi_accrual, :local_pause, :start] on rising edge
• [:phi_accrual, :local_pause, :stop] on falling edge

Caveat: Only one system_monitor can be installed per node. If your application already uses :erlang.system_monitor/2, disable this module via config :phi_accrual, pause_monitor: false and feed pause state in yourself by calling put_state/1.