Fix mergerfs pool consolidation and naming

- Improve pool name extraction in dashboard parsing
- Use consistent mergerfs pool naming in agent
- Add mount_point metric parsing to use actual mount paths
- Fix pool consolidation to prevent duplicate entries

agent/src/collectors/disk.rs

@@ -781,7 +781,13 @@ impl DiskCollector {
         timestamp: u64,
         status_tracker: &mut StatusTracker
     ) {
-        let pool_name = pool.mount_point.trim_start_matches('/').replace('/', "_");
+        // Use consistent pool naming: extract mount point without leading slash
+        let pool_name = if pool.mount_point == "/" {
+            "root".to_string()
+        } else {
+            pool.mount_point.trim_start_matches('/').replace('/', "_")
+        };
+        
         if pool_name.is_empty() {
             return;
         }