docs: add circuit breaker metrics counters

Author: mfkd

content/master/guides/metrics.md

@@ -55,4 +55,7 @@ prometheus.io/scrape: "true"
 | {{<hover label="crossplane_managed_resource_first_time_to_readiness_seconds_bucket" line="27">}}crossplane_managed_resource_first_time_to_readiness_seconds_bucket{{</hover>}} | The time it took for a managed resource to become ready first time after creation |  |
 | {{<hover label="crossplane_managed_resource_first_time_to_reconcile_seconds_bucket" line="28">}}crossplane_managed_resource_first_time_to_reconcile_seconds_bucket{{</hover>}} | The time it took to detect a managed resource by the controller |  |
 | {{<hover label="upjet_resource_ttr_bucket" line="29">}}upjet_resource_ttr_bucket{{</hover>}} | Measures in seconds the `time-to-readiness` `(TTR)` for managed resources |  |
+| {{<hover label="crossplane_circuit_breaker_opens_total" line="30">}}crossplane_circuit_breaker_opens_total{{</hover>}} | Total number of times the XR watch circuit breaker opened | Each increase indicates a controller that temporarily stopped processing watched events. |
+| {{<hover label="crossplane_circuit_breaker_closes_total" line="31">}}crossplane_circuit_breaker_closes_total{{</hover>}} | Total number of times the XR watch circuit breaker closed again | Compare with opens to monitor how quickly controllers recover from watch pressure. |
+| {{<hover label="crossplane_circuit_breaker_events_total" line="32">}}crossplane_circuit_breaker_events_total{{</hover>}} | Total number of watched events handled by the XR circuit breaker | Includes a `result` label (`allowed`, `dropped`, or `halfopen_allowed`) that shows how events were treated. |
 {{</table >}}