feat(sidebar): add interactive drag-to-open gesture

Sidebar now follows the finger during swipe-to-open gesture from anywhere
on the screen. Uses shared animation context between AppContainer and
SlidingSidebar for synchronized translateX values.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/app/src/components/agent-list.tsx

@@ -221,6 +221,7 @@ export function AgentList({ agents, isRefreshing = false, onRefresh, selectedAge
 const styles = StyleSheet.create((theme) => ({
   list: {
     flex: 1,
+    minHeight: 0,
   },
   listContent: {
     paddingHorizontal: theme.spacing[4],