Podcast workflow: assign lanes by hand, match by season, unique keys for unseasoned episodes; drop old checklist data file; v2.16.0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitignore

@@ -55,3 +55,7 @@ data/study-community.json
 data/analytics-events.json
 data/admin-reply-history.json
 data/episode-plays.json
+
+# Episode workflow progress — lives only in the server data volume
+data/podcast-workflow.json
+data/nuggets-workflow.json