fix(db): define the legacy purge without running it

supabase/README.md

@@ -123,7 +123,7 @@ The database gate proves migration replay and pgTAP assertions locally. It does
 
 `20260927170000_debate_context_pins.sql` is additive: it creates `debate_context_pins`, the saved results a student pins per debate, with RLS and a composite key to the owner's debate.
 
-`20260926090100_legacy_debate_cleanup.sql` is destructive and one-time: it deletes legacy results, chats, flowcharts, sparring rounds, and sources that belong to no debate and had no activity in the 30 days before `20260926090000_current_debates.sql` recorded its rollout time in `private.current_debate_rollout`. Work created after that time is never touched, however late the cleanup runs. Keep it separate from the additive `20260926090000_current_debates.sql`, and apply it to a remote project only with explicit authorization for that environment.
+`20260926090100_legacy_debate_cleanup.sql` defines `private.purge_legacy_debate_material`, which deletes legacy results, chats, flowcharts, sparring rounds, and sources that belong to no debate and had no activity in the 30 days before `20260926090000_current_debates.sql` recorded its rollout time in `private.current_debate_rollout`. The migration does not call it, so applying it deletes nothing; legacy rows stay in the Unsorted view. Running the purge on a remote project is a separate, destructive step that needs explicit authorization for that environment. Work created after the rollout is never touched, however late it runs.
 
 ## Edge Function tests
 

supabase/migrations/20260926090100_legacy_debate_cleanup.sql

@@ -1,14 +1,19 @@
--- DESTRUCTIVE, ONE-TIME: remove legacy material that predates Current Debate
--- and had no activity in the 30 days before it shipped. Recent legacy material
--- stays, without a debate, in the Unsorted view until the user confirms where
--- it belongs.
+-- One-time purge of legacy material that predates Current Debate and had no
+-- activity in the 30 days before it shipped. This migration only defines the
+-- function; it does not run it. Adam chose on 2026-09-30 to keep production's
+-- legacy material, so any purge is a separate, explicitly authorized call:
 --
--- Only rows with no debate that were created before the rollout are candidates,
--- so neither debate work nor later one-off work can be removed, however late
--- this runs. Nothing schedules it; this migration calls it once. Activity is
--- the latest edit where a table records one (flowcharts, sparring sessions) and
--- the latest message for chats. Chat messages and source files go with their
--- parents through ON DELETE CASCADE; evidence cards keep a null source.
+--   SELECT private.purge_legacy_debate_material(
+--     (SELECT started_at FROM private.current_debate_rollout)
+--   );
+--
+-- Until then, legacy material stays, without a debate, in the Unsorted view.
+-- Only rows with no debate that were created before the rollout are
+-- candidates, so neither debate work nor later one-off work can be removed,
+-- however late it runs. Activity is the latest edit where a table records one
+-- (flowcharts, sparring sessions) and the latest message for chats. Chat
+-- messages and source files go with their parents through ON DELETE CASCADE;
+-- evidence cards keep a null source.
 
 CREATE FUNCTION private.purge_legacy_debate_material(p_rollout timestamptz)
 RETURNS void
@@ -39,7 +44,3 @@ $$;
 
 REVOKE ALL ON FUNCTION private.purge_legacy_debate_material(timestamptz)
   FROM PUBLIC, anon, authenticated, service_role;
-
-SELECT private.purge_legacy_debate_material(
-  (SELECT started_at FROM private.current_debate_rollout)
-);