docs: clarify instructions for generating release notes

Author: dkattan

.github/prompts/release-notes.md

@@ -11,6 +11,8 @@ ${{ steps.context.outputs.stats }}
 
 Task:
 Generate release notes for version ${{ steps.version.outputs.version }}.
+Given the previous tag above look at the _actual code changes_ by each commit
+You may need to use subagents or go commit by commit if the changes are large as to not blowout your context window.
 The release notes should be in Markdown format.
 Include:
 - A summary of changes.