STATE-WP-0072: stop dual-writing workstream_id on decisions

Record decision scope with workplan_id only to avoid legacy-meter
body alias hits on POST /decisions/.

session_memory/curate/decisions.py

@@ -49,7 +49,6 @@ def build_decision(candidate: dict, action: str, rationale: str,
     }
     if scope_id:
         payload["workplan_id"] = scope_id
-        payload["workstream_id"] = scope_id
     return payload
 
 

tests/test_curate_decisions.py

@@ -19,7 +19,7 @@ def test_build_decision_payload_shape():
     d = build_decision(_candidate(), "approve", "looks solid", workplan_id="wp-1")
     assert d["decision_type"] == "made"
     assert d["workplan_id"] == "wp-1"
-    assert d["workstream_id"] == "wp-1"
+    assert "workstream_id" not in d
     assert "Promote" in d["title"]
     assert d["rationale"] == "looks solid"
     assert "success:clean_pass:outcome" in d["description"]