Add SPC convective outlook data contracts

docs/internal/module.md

@@ -45,6 +45,10 @@ The registry recognizes these IDs:
 Every registered module has a builder. Report composition entries that refer to
 unknown or unimplemented module IDs fail validation instead of being skipped.
 
+The package also defines `spc_convective_outlooks` and
+`spc_convective_discussion` IDs and empty option structs for the collected
+contract. They are not registered modules in the briefing registry.
+
 ## Options
 
 Most modules use an empty options struct. `area_forecast_discussion` accepts: