Location params on best_local_bid / latest_prices (zip / GPS + radius)

Thread zip/lat/lng/radius_miles through the client and both tools; friendly
guard for the zip-XOR-gps rule. Formatters surface distance, the searched
center, and the nearest-source hint when nothing is in range.

- client: best()/latest() take zip/lat/lng/radius_miles
- server: location params + docstrings (note Ohio-concentrated coverage)
- format: distance column + center/nearest rendering
- README + CHANGELOG + advisor prompt library updated
- tests: location formatting cases

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

ag_bids_mcp/client.py

@@ -54,9 +54,12 @@ def _get(path: str, **params: Any) -> dict | list:
 
 
 def latest(commodity: str | None = None, source: str | None = None,
-           delivery: str | None = None, kind: str | None = None) -> dict:
+           delivery: str | None = None, kind: str | None = None,
+           zip: str | None = None, lat: float | None = None,
+           lng: float | None = None, radius_miles: float | None = None) -> dict:
     return _get("/api/data/latest",
-                commodity=commodity, source=source, delivery=delivery, kind=kind)
+                commodity=commodity, source=source, delivery=delivery, kind=kind,
+                zip=zip, lat=lat, lng=lng, radius_miles=radius_miles)
 
 
 def history(commodity: str | None = None, source_id: int | None = None,
@@ -66,8 +69,10 @@ def history(commodity: str | None = None, source_id: int | None = None,
                 delivery=delivery, days=days)
 
 
-def best(commodity: str) -> dict:
-    return _get("/api/data/best", commodity=commodity)
+def best(commodity: str, zip: str | None = None, lat: float | None = None,
+         lng: float | None = None, radius_miles: float | None = None) -> dict:
+    return _get("/api/data/best", commodity=commodity,
+                zip=zip, lat=lat, lng=lng, radius_miles=radius_miles)
 
 
 def price_trend(commodity: str, geo: str = "US", years: int = 10) -> dict: