Add report generation mode metadata

docs/internal/report-registry.md

@@ -16,6 +16,7 @@ Each report definition declares:
 
 - report ID and display name
 - Scriptorium prompt ID
+- generation mode
 - valid-period resolver
 - comparison strategy
 - managed artifact group
@@ -25,6 +26,10 @@ Each report definition declares:
 - morning or evening batch membership
 - default ordered module composition
 
+Current report definitions use the `scriptorium_markdown` generation mode.
+Template and structured-text schema identifiers are empty for these Markdown
+reports.
+
 ## Reports
 
 | Report | ID | Prompt | Artifact group | Batch copy | Prior compatibility |