chore(telemetry): drop http_server body-size histograms via OTel views

The http.server.{request,response}.body.size histograms are
auto-instrumented by otelhttp and pushed OTLP-direct to Grafana Cloud
(bypassing Alloy), so they can't be dropped with a chart-side relabel.
They account for ~700 active series and back no panels.

Register sdkmetric.NewView for each, applying AggregationDrop{}, on the
OTLP MeterProvider. The http.server.request.duration histogram is left
untouched — its buckets back the p50/p95/p99 latency panels.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dmerrick

pkg/telemetry/telemetry.go

@@ -83,11 +83,13 @@ func Init(ctx context.Context, serviceName, serviceVersion string) (ShutdownFunc
 	if err != nil {
 		return noopShutdown, fmt.Errorf("prometheus exporter: %w", err)
 	}
-	mp := sdkmetric.NewMeterProvider(
+	mpOpts := []sdkmetric.Option{
 		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(metricExp)),
 		sdkmetric.WithReader(promExp),
 		sdkmetric.WithResource(res),
-	)
+	}
+	mpOpts = append(mpOpts, dropBodySizeHistograms()...)
+	mp := sdkmetric.NewMeterProvider(mpOpts...)
 	otel.SetMeterProvider(mp)
 
 	if err := otelruntime.Start(otelruntime.WithMinimumReadMemStatsInterval(15 * time.Second)); err != nil {
@@ -141,6 +143,26 @@ func Init(ctx context.Context, serviceName, serviceVersion string) (ShutdownFunc
 	}, nil
 }
 
+// dropBodySizeHistograms returns MeterProvider options that drop the
+// http_server_{request,response}_body_size_bytes histograms via OTel SDK
+// views. These auto-instrumented histograms are pushed OTLP-direct to the
+// metrics backend (bypassing Alloy, so they can't be relabeled chart-side)
+// and account for ~700 active series with no panels reading them. The
+// http_server_request_duration_seconds histogram is deliberately left
+// untouched — its buckets back the p50/p95/p99 latency panels.
+func dropBodySizeHistograms() []sdkmetric.Option {
+	drop := func(name string) sdkmetric.Option {
+		return sdkmetric.WithView(sdkmetric.NewView(
+			sdkmetric.Instrument{Name: name},
+			sdkmetric.Stream{Aggregation: sdkmetric.AggregationDrop{}},
+		))
+	}
+	return []sdkmetric.Option{
+		drop("http.server.request.body.size"),
+		drop("http.server.response.body.size"),
+	}
+}
+
 func disabled() bool {
 	switch strings.ToLower(os.Getenv("OTEL_SDK_DISABLED")) {
 	case "true", "1", "yes":