[router] Add rustfmt and set group imports by default (#11732)

sgl-router/src/tokenizer/sequence.rs

@@ -1,7 +1,9 @@
-use super::traits::{TokenIdType, Tokenizer as TokenizerTrait};
-use anyhow::Result;
 use std::sync::Arc;
 
+use anyhow::Result;
+
+use super::traits::{TokenIdType, Tokenizer as TokenizerTrait};
+
 /// Maintains state for an ongoing sequence of tokens and their decoded text
 /// This provides a cleaner abstraction for managing token sequences
 pub struct Sequence {