WeatherTool: use Russian query for Celsius sources

'погода Балашиха сейчас' returns Russian weather sites (gismeteo,
meteotrend) that report in °C, vs English queries which return
Fahrenheit snippets that the model misreads as Celsius.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fast_tools.py

@@ -52,7 +52,7 @@ class WeatherTool(FastTool):
     )
 
     # Fixed query — always fetch home location weather
-    _SEARCH_QUERY = "weather Balashikha Moscow now"
+    _SEARCH_QUERY = "погода Балашиха сейчас"  # Russian query → Celsius sources
 
     def __init__(self, searxng_url: str):
         self._searxng_url = searxng_url
@@ -81,7 +81,7 @@ class WeatherTool(FastTool):
             return ""
 
         # Prefer results whose snippets contain actual current conditions
-        lines = ["Current weather data for Balashikha, Moscow region:\n"]
+        lines = ["Current weather data for Balashikha, Moscow region (temperatures in °C):\n"]
         for item in items:
             snippet = item.get("content", "")
             title = item.get("title", "")