docs(mimic-iv): add chartevents-after-outtime audit query

Give researchers a concrete count for the #1961 offset pattern.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Chessing234

mimic-iv/concepts/documentation/chartevents_after_outtime.sql

@@ -0,0 +1,13 @@
+-- Count chartevents whose charttime falls after the linked ICU stay outtime.
+-- Useful as a sensitivity check when building in-ICU only cohorts (#1961).
+
+SELECT
+  COUNT(*) AS chartevents_rows,
+  COUNT(*) FILTER (WHERE ce.charttime > ie.outtime) AS after_outtime,
+  COUNT(*) FILTER (
+    WHERE ce.charttime > ie.outtime
+      AND ce.charttime <= ie.outtime + INTERVAL '6 hours'
+  ) AS after_outtime_within_6h
+FROM icu.chartevents AS ce
+INNER JOIN icu.icustays AS ie
+  ON ce.stay_id = ie.stay_id;