Remove unused alert envelope retention

docs/internal/briefing.md

@@ -48,6 +48,8 @@ metadata summary, checked-empty alerts and SPC outlooks remain distinct from
 missing sources, and prompt-safe SPC values omit geometry and other
 template-only or source details. The complete module composition is in
 [module internals](module.md); fact derivation is in [fact contracts](facts.md).
+Alert digests are built from selected alert items and source provenance, not a
+provider response envelope.
 
 Derived daypart-summary maps use the forecast package's canonical daypart
 identity and reject any collision instead of replacing an earlier value.

docs/internal/facts.md

@@ -16,6 +16,9 @@ story, and convective outlook data. Source provenance and warnings are copied
 into their own slices so downstream consumers can inspect data completeness
 without treating it as an ordinary weather fact.
 
+Alert facts retain individual alert payloads for period selection together with
+their copied source provenance; they do not retain a provider response envelope.
+
 A nil bundle produces an empty collected value. Collection itself, missing
 source policy, and source hashes are outside this package.
 

docs/internal/weather-data.md

@@ -31,6 +31,10 @@ provider endpoint or retry policy from the normalized types. See
 [collection](collect.md) for assembly and
 [report templates](../templates.md) for the values exposed to authors.
 
+An alert run retains its check time and individual alert payloads for overlap
+selection. Its source entry retains provider provenance; the full provider
+envelope is not carried into the normalized bundle.
+
 ## Source provenance
 
 Every checked source is represented by a `Source` entry. The record identifies