STATE-WP-0069: MCP Phase 1 deprecation + open_workplans summary alias

Complete MCP legacy deprecation coverage (resource + docstrings + TOOLS.md).
Dual-write open_workplans on /state/summary alongside open_workstreams;
get_domain_summary prefers the new key. T06 internal rename started.

tests/test_routers_core.py

@@ -430,6 +430,8 @@ class TestStateSummary:
         assert r.status_code == 200
         body = r.json()
         assert "open_workstreams" in body
+        assert "open_workplans" in body
+        assert body["open_workplans"] == body["open_workstreams"]
         assert "blocking_decisions" in body
         assert "blocked_tasks" in body
         assert "domains" in body