Add futures_quote tool: CBOT price + change since open + on day

New futures_quote(commodity, delivery?) tool wraps the new /api/data/futures
endpoint: reports latest price, today's session open, prior settle, and both
moves (since open and on the day). With a delivery month it resolves the listed
contract; without it, the continuous nearby. Adds client.futures(), fmt_futures(),
tests, and a CHANGELOG entry.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_client.py

@@ -71,6 +71,29 @@ def test_get_drops_none_params(monkeypatch):
     assert captured["params"] == {"commodity": "corn"}
 
 
+def test_futures_endpoint_params(monkeypatch):
+    client = _reload_client(monkeypatch)
+    captured = {}
+
+    class FakeResp:
+        status_code = 200
+        text = ""
+        def json(self): return {"quote": None}
+
+    def fake_get(url, params=None, timeout=None, headers=None):
+        captured["url"] = url
+        captured["params"] = dict(params or {})
+        return FakeResp()
+
+    monkeypatch.setattr(client.httpx, "get", fake_get)
+    client.futures(commodity="corn", delivery="Jul 2026")
+    assert captured["url"].endswith("/api/data/futures")
+    assert captured["params"] == {"commodity": "corn", "delivery": "Jul 2026"}
+    # delivery omitted → dropped
+    client.futures(commodity="corn")
+    assert captured["params"] == {"commodity": "corn"}
+
+
 def test_history_without_commodity_drops_param(monkeypatch):
     client = _reload_client(monkeypatch)
     captured = {}

tests/test_format.py

@@ -35,6 +35,46 @@ def test_fmt_best_no_winner():
     assert "wheat" in out
 
 
+def test_fmt_futures_with_changes():
+    payload = {
+        "commodity": "corn", "delivery": "Jul 2026", "contract": "ZCN26",
+        "symbol": "ZC",
+        "quote": {
+            "settle_date": "2026-05-29", "open_cents": 461, "last_cents": 455,
+            "prev_close_cents": 460, "change_since_open_cents": -6,
+            "change_on_day_cents": -5, "fetched_at": "2026-05-29T18:00:00+00:00",
+        },
+    }
+    out = fmt.fmt_futures(payload)
+    assert "ZCN26" in out and "Jul 2026" in out
+    assert "$4.5500" in out   # last
+    assert "$4.6100" in out   # open
+    assert "▼ -0.06" in out   # change since open
+    assert "▼ -0.05" in out   # change on day
+
+
+def test_fmt_futures_no_open_yet():
+    payload = {
+        "commodity": "soy", "delivery": None, "contract": "continuous",
+        "symbol": "ZS=F",
+        "quote": {
+            "settle_date": "2026-05-29", "open_cents": None, "last_cents": 1180,
+            "prev_close_cents": 1177, "change_since_open_cents": None,
+            "change_on_day_cents": 3, "fetched_at": "2026-05-29T18:00:00+00:00",
+        },
+    }
+    out = fmt.fmt_futures(payload)
+    assert "continuous nearby" in out
+    assert "no open captured yet" in out
+    assert "▲ +0.03" in out  # change on day still shown
+
+
+def test_fmt_futures_no_quote():
+    out = fmt.fmt_futures({"commodity": "wheat", "delivery": None,
+                           "contract": "continuous", "quote": None})
+    assert "No futures quote on file" in out
+
+
 def test_fmt_inputs_lime_table():
     payload = {
         "product": "lime", "count": 2,