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>

ag_bids_mcp/format.py

@@ -90,6 +90,41 @@ def fmt_best(commodity: str, payload: dict) -> str:
     )
 
 
+# ---------- futures quote + change ----------
+
+
+def fmt_futures(payload: dict) -> str:
+    commodity = payload.get("commodity")
+    delivery = payload.get("delivery")
+    contract = payload.get("contract")
+    q = payload.get("quote")
+    scope = f"{commodity} {contract}" + (f" ({delivery})" if delivery else " (continuous nearby)")
+    if not q:
+        return f"### CBOT futures — {scope}\n\nNo futures quote on file yet for this contract.\n"
+
+    last = q.get("last_cents")
+    open_c = q.get("open_cents")
+    prev = q.get("prev_close_cents")
+    d_open = q.get("change_since_open_cents")
+    d_day = q.get("change_on_day_cents")
+
+    lines = [f"### CBOT futures — {scope}", ""]
+    lines.append(f"- **Last**: {_bu(last)}  _(settle/last for {q.get('settle_date') or '?'})_")
+    if open_c is not None:
+        lines.append(f"- **Open**: {_bu(open_c)}")
+    if prev is not None:
+        lines.append(f"- **Prev close**: {_bu(prev)}")
+    if d_open is not None:
+        lines.append(f"- **Change since open**: {_delta_arrow(d_open)} {_basis(d_open)}")
+    else:
+        lines.append("- **Change since open**: — (no open captured yet)")
+    if d_day is not None:
+        lines.append(f"- **Change on day**: {_delta_arrow(d_day)} {_basis(d_day)}")
+    else:
+        lines.append("- **Change on day**: — (no prior settle yet)")
+    return "\n".join(lines) + "\n"
+
+
 # ---------- inputs / fertilizer ----------