Correct derived briefing weather semantics

docs/internal/briefing.md

@@ -32,6 +32,13 @@ discussion, and weather story. Derived builders shape daily and daypart
 summaries, precipitation timing, outdoor windows, and the report-specific
 Daily, Today, and Tomorrow planning values.
 
+The daily summary preserves generic feels-like values as
+`apparent_temperature_max_f`; it does not label them as a heat index. Daypart
+temperature phrases retain below-zero meaning, including through temperature
+trends that cross zero. Outdoor windows add a 25-point risk penalty and an
+explicit reason for each snow, ice, or fog indicator. Equal scores retain input
+order for both best and worst windows.
+
 The module registry preserves rich values for templates and snapshots while
 curating prompt exports where needed. In particular, source warnings are a
 metadata summary, checked-empty alerts and SPC outlooks remain distinct from