release: add behavioral feature-gate coverage

RELEASE_NOTES.md

@@ -77,6 +77,11 @@ AAS-oriented 2.0 API:
   minute no longer makes a healthy rollup fall back to raw. Completeness when a
   window starts before physical raw coverage remains tracked by issue #122.
   ([PR #199](https://github.com/NikolayS/pg_ash/pull/199))
+- **Report windows now floor subsecond endpoints before epoch conversion.**
+  `ash.report()` no longer shifts a request made in the final half-second of a
+  minute into the next minute, so its coverage bounds and data-bearing minute
+  count remain aligned with the documented minute floor.
+  ([PR #192](https://github.com/NikolayS/pg_ash/pull/192))
 
 ## Retired tooling
 

devel/docker/Dockerfile

@@ -0,0 +1,26 @@
+# pg_cron-capable PostgreSQL image for the release gate.
+#
+# Keep the image tag separate from PostgreSQL's numeric major. In particular,
+# postgres:19beta2 exports PG_MAJOR=19, which is the value required by the
+# postgresql-19-cron package name.
+ARG POSTGRES_TAG=18
+FROM postgres:${POSTGRES_TAG}
+
+# pg_cron versions differ by PostgreSQL major and follow the pinned base
+# image's PGDG repository snapshot.
+# hadolint ignore=DL3008
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends "postgresql-${PG_MAJOR}-cron" \
+ && rm -rf /var/lib/apt/lists/*
+
+# initdb copies this sample into each new cluster, so both libraries are loaded
+# on first start. cron.database_name is intentionally not baked in: callers can
+# select the database at runtime with:
+#
+#   postgres -c cron.database_name=<database>
+RUN printf '%s\n' \
+    '' \
+    '# pg_ash release-gate defaults' \
+    "shared_preload_libraries = 'pg_cron,pg_stat_statements'" \
+    'cron.use_background_workers = on' \
+    >> /usr/share/postgresql/postgresql.conf.sample