[SIMPL-30451] Close the distributed execution reference service

Check the chart's actual DAGSTER_PG_PASSWORD injection in the tightly coupled preflight instead of DAGSTER_POSTGRES_*, which the Simpl chart never sets; the old check warned about a misconfiguration on a correctly configured run pod. Evidence reports the variable name only, never its value.

Record the platform k8s_job_executor run as cluster-verified in the guide and readiness checklist, add the Dagster UI screenshots covering job list, graph, code-configured tags and a successful run.

Changelog: fixed

tests/test_tightly_coupled.py

@@ -81,6 +81,16 @@ def test_env_var_check_reports_missing_names():
     assert result["missing"] == ["DEFINITELY_NOT_SET_12345"]
 
 
+def test_env_var_check_reports_present_names(monkeypatch):
+    monkeypatch.setenv("DAGSTER_PG_PASSWORD", "not-exposed-in-evidence")
+
+    result = check_env_vars(("DAGSTER_PG_PASSWORD",))
+
+    assert result["passed"] is True
+    assert result["present"] == ["DAGSTER_PG_PASSWORD"]
+    assert "not-exposed-in-evidence" not in repr(result)
+
+
 def test_pod_identity_falls_back_outside_kubernetes(monkeypatch):
     monkeypatch.delenv("DAGSTER_K8S_PIPELINE_RUN_NAMESPACE", raising=False)