[Router] Add bucket-aware policy domains and native cache indexing (#38108)

Signed-off-by: Vincent Gao <vincentbo@linux.alibaba.com>
Co-authored-by: inkcherry <mingzhi.liu@amd.com>
Co-authored-by: yangbodong22011 <13137470+yangbodong22011@users.noreply.github.com>

experimental/sgl-router/monitoring/README.md

@@ -25,7 +25,6 @@ The dashboard graphs every family the router emits:
 | `sgl_router_worker_requests_total` | Counter | Per-worker **dispatches** by `worker_url`, `model_id`, `mode`, `outcome` (recorded after dispatch; blind to pre-dispatch drops) |
 | `sgl_router_request_duration_seconds` | Histogram | End-to-end request latency by `model_id` |
 | `sgl_router_ttft_seconds` | Histogram | Time to first token (streaming) by `model_id` |
-| `sgl_router_overlap_blocks` | Histogram | Cache-aware-zmq overlap blocks by `model_id` |
 | `sgl_router_active_load` | Gauge | Per-worker prefill-token / decode-block load |
 | `sgl_router_workers` | Gauge | Registered worker count by `mode` |
 | `sgl_router_worker_health` | Gauge | Per-worker health (1=breaker admits, 0=open) |
@@ -35,6 +34,10 @@ The dashboard graphs every family the router emits:
 | `sgl_router_decode_affinity_total` | Counter | PD decode-affinity outcomes |
 | `sgl_router_sticky_total` | Counter | Sticky-session selection outcomes |
 
+The legacy `sgl_router_overlap_blocks` metric was removed with the
+`cache_aware_zmq` policy and has no direct replacement. Remove queries, alerts,
+and dashboard panels that depend on this metric before upgrading.
+
 The `sgl_router_workers` / `sgl_router_worker_*` gauges are sampled from the
 live worker registry on every scrape, so a removed worker stops emitting
 series immediately rather than leaving a stale value.