Add search filter and expand/collapse to find page

- Find page now has same controls as files page
- Both pages support expand all / collapse all buttons
- FileSystem component accepts controlled expandAll state
- Fixed single-key groups to not show as collapsible

.gitignore

@@ -34,3 +34,4 @@ yarn-error.log*
 
 *.tsbuildinfo
 next-env.d.ts
+.playwright-mcp/