docs: document ZFS pool health alerting; fix pushover sound+url_title

hbd/config_thresholds_example.yaml

@@ -134,6 +134,29 @@ thresholds:
           hysteresis: 0.1
           enabled: true
   
+  # ----------------------------------------------------------------------------
+  # ZFS Monitor Thresholds
+  # ----------------------------------------------------------------------------
+  zfs_monitor:
+    # Pool health check — built-in default; shown here for reference/override.
+    # health_ok is 1 (ONLINE) or 0 (DEGRADED, SUSPENDED, FAULTED, UNAVAIL…).
+    # Use '*' to apply the same rule to every pool, or name a specific pool.
+    pools:
+      '*':
+        health_ok:
+          critical: 1           # Alert CRITICAL when pool is not ONLINE
+          operator: "<"
+          hysteresis: 0.0       # No hysteresis — a degraded pool is always critical
+          display: "ZFS pool {pool_name} is {health}"
+
+      # Per-pool capacity thresholds (optional; add pools you care about)
+      # tank:
+      #   capacity:
+      #     warning: 75.0       # Warn at 75% used
+      #     critical: 90.0      # Critical at 90% used
+      #     operator: ">"
+      #     hysteresis: 0.05
+
   # ----------------------------------------------------------------------------
   # Network Monitor Thresholds
   # ----------------------------------------------------------------------------