feat(dynamic-sampling): Record EAP and outcomes volume in sliding-window comparison

Emit dynamic_sampling.per_org.sliding_window.eap_volume and .outcomes_volume alongside
the existing sample-rate metrics so the volumes behind each computed rate can be compared
directly.

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

Author: shellmayr

src/sentry/dynamic_sampling/per_org/calculations.py

@@ -95,6 +95,20 @@ def sample_rate_for(volume: OrganizationDataVolume | None) -> float | None:
             sample_rate=1.0,
             tags=tags,
         )
+    if eap_volume is not None:
+        metrics.distribution(
+            f"{SLIDING_WINDOW_METRIC_PREFIX}.eap_volume",
+            eap_volume.total,
+            sample_rate=1.0,
+            tags=tags,
+        )
+    if outcomes_volume is not None:
+        metrics.distribution(
+            f"{SLIDING_WINDOW_METRIC_PREFIX}.outcomes_volume",
+            outcomes_volume.total,
+            sample_rate=1.0,
+            tags=tags,
+        )
 
 
 def run_project_balancing(