Compare recent changes from module snapshots

docs/internal/changes.md

@@ -4,15 +4,15 @@ This document describes structured Recent Changes comparison.
 
 ## Purpose
 
-`internal/changes` compares current and prior briefing packages and emits
+`internal/changes` compares current and prior module snapshots and emits
 compact change records for prompt input data packages.
 
 ## Inputs And Outputs
 
 Inputs:
 
-- prior briefing package
-- current briefing package
+- prior module snapshot
+- current module snapshot
 - comparison thresholds from configuration
 
 Outputs:
@@ -22,7 +22,7 @@ Outputs:
 
 ## Boundaries
 
-- This package compares structured briefing data only.
+- This package compares structured module snapshot data only.
 - It does not read filesystem state, find prior snapshots, render Markdown,
   invoke Scriptorium, or compare generated report text.
 
@@ -41,7 +41,7 @@ None.
 
 ## State Or Manifest Behavior
 
-None directly. The app loads prior briefing snapshots through `internal/state`
+None directly. The app loads prior module snapshots through `internal/state`
 before calling comparison functions.
 
 ## Skip And Resume Behavior
@@ -51,9 +51,11 @@ empty Recent Changes list without calling a comparison function.
 
 ## Failure Behavior
 
-- Daily comparison requires both inputs to contain Daily briefing content.
-- 3-Day comparison requires both inputs to contain 3-Day briefing content.
-- Weekend comparison requires both inputs to contain Weekend briefing content.
+- Daily comparison requires `derived_daily_summary` and
+  `derived_daypart_summaries` stanzas. It also uses `alert_digest` and
+  `precip_timing` when present.
+- 3-Day comparison requires `derived_daypart_summaries`.
+- Weekend comparison requires `derived_daypart_summaries`.
 - Storm Report currently has no comparison implementation, so the app leaves
   Recent Changes empty for Storm reports.