docs: add release-note fragment for PR #2184

Signed-off-by: llm-d-router-release-notes[bot] <287676111+llm-d-router-release-notes[bot]@users.noreply.github.com>

Author: llm-d-router-release-notes[bot]

release-notes.d/unreleased/2184.md

@@ -0,0 +1,7 @@
+---
+pr: 2184
+url: https://github.com/llm-d/llm-d-router/pull/2184
+author: sudoalok
+date: 2026-08-19
+---
+Added flow control capacity utilization gauges. `llm_d_epp_flow_control_capacity_utilization_requests` and `llm_d_epp_flow_control_capacity_utilization_bytes` report occupancy as a fraction of a priority band's effective capacity (0.0-1.0), labelled by `priority` and `inference_pool`. `llm_d_epp_flow_control_global_capacity_utilization_requests` and `llm_d_epp_flow_control_global_capacity_utilization_bytes` report the all-bands rollup, emitted only when a global capacity is configured. Operators can alert on "band at N% of its limit" without joining config values into PromQL.