Fix logic conflicts (supabase#40362)

When applying these rules to my personal project. My cursor bug bot detected logical gaps in these 2 prompts.

Author: smeubank

examples/prompts/database-rls-policies.md

@@ -30,7 +30,9 @@ The output should use the following instructions:
 The output should look like this:
 
 ```sql
-CREATE POLICY "My descriptive policy." ON books FOR INSERT to authenticated USING ( (select auth.uid()) = author_id ) WITH ( true );
+CREATE POLICY "My descriptive policy." ON books
+  FOR INSERT TO authenticated
+  WITH CHECK ((select auth.uid()) = author_id);
 ```
 
 Since you are running in a Supabase environment, take note of these Supabase-specific additions below.

examples/prompts/use-realtime.md

@@ -415,7 +415,7 @@ CREATE POLICY "users_can_receive_broadcasts" ON realtime.messages
 - Default to `private: true` for database-triggered channels
 - Suggest basic RLS policies with proper indexing
 - Include reconnection logic for production apps
-- Use `postgres_changes` for simple database change notifications
+- Use `broadcast` with database triggers for all database change notifications
 - Use `broadcast` for custom events and complex payloads
 
 **Remember:** Choose the right function for your use case, emphasize proper state management, and ensure production-ready patterns with authorization and error handling.