Feed DataSource Expert - Paged Lists & Infinite Scroll

What: Pattern for paginated, reactive list/feed widgets using ValueNotifiers and Commands. Integrates with proxy pattern for entity lifecycle management.

CRITICAL RULES

• Auto-pagination triggers at items.length - 3 (not at the last item)
• updateDataCommand for initial/refresh loads, requestNextPageCommand for pagination - separate commands
• When refreshing with proxies: release OLD proxies AFTER replacing with new ones (delay release for animations)
• itemCount is a ValueNotifier - watch it to rebuild the list widget
• Feed data sources are typically created with createOnce in widgets, NOT registered in get_it
• getItemAtIndex(index) both returns the item AND triggers auto-pagination

Base FeedDataSource

Non-paged feed for finite data sets: