Update weather reports to remove the unused confidence field

prompts/pipeline-weather/today/today_generated_text.user.md

@@ -11,7 +11,6 @@ Return these fields:
 - `summary`: required. 1-2 sentences summarizing the main weather story for the valid period.
 - `forecast_discussion`: required. 3 paragraphs explaining the broader setup, trend, and/or forecast reasoning most relevant to the valid period.
 - `precipitation_timing`: optional. Include only when the deterministic `precip_timing` module contains precipitation windows. 
-- `confidence`: optional. Include only if uncertainty, timing spread, or conflicting signals materially affect how the reader should interpret the forecast.
 
 Return JSON only.
 
@@ -51,7 +50,7 @@ In most cases, the `forecast_discussion` should include three paragraphs:
 
 # precipitation_timing
 
-Use 1-2 sentences to add practical context, including:
+Optional. Return only if precipitation is forecast. If present, provide 1 to 4 sentences to add practical context, including:
 
   - Whether the precipitation is associated with a moving frontal boundary, convective initiation, or wide stratiform rain (if this can be determined from the data package);
   - The expected type, intensity, and duration of the precipitation; and