fix(turbopack): Fix a panic when the generated hash is too short when radix formatting a string. (#80966)

## Fix hash length check in metadata formatting

### What?
Fixed a panic in the `format_radix` function when the generated hash is
shorter than 6 characters.

### Why?
The current implementation always tries to take the first 6 characters
of the hash using a fixed slice `result[..6]`, which would panic if the
hash is shorter than 6 characters. This doesn't match the JavaScript
behavior where `toString(36).slice(0, 6)` automatically takes the
minimum of the hash length and 6.

### How?
Added a check to determine the minimum length between the hash length
and 6, then use that value for slicing:
```rust
let len = result.len().min(6);
result[..len].iter().collect()
```

Fixes #PACK-4495

Author: Cy-Tek

crates/next-core/src/next_app/metadata/mod.rs

@@ -276,7 +276,12 @@ fn format_radix(mut x: u32, radix: u32) -> String {
     }
 
     result.reverse();
-    result[..6].iter().collect()
+
+    // We only need the first 6 characters of the hash but sometimes the hash is too short.
+    // In JavaScript, we use `toString(36).slice(0, 6)` to get the first 6 characters of the hash,
+    // but it will automatically take the minimum of the length of the hash and 6. Rust will panic.
+    let len = result.len().min(6);
+    result[..len].iter().collect()
 }
 
 /// If there's special convention like (...) or @ in the page path,
@@ -360,7 +365,7 @@ pub fn normalize_metadata_route(mut page: AppPage) -> Result<AppPage> {
 
 #[cfg(test)]
 mod test {
-    use super::normalize_metadata_route;
+    use super::{djb2_hash, format_radix, normalize_metadata_route};
     use crate::next_app::AppPage;
 
     #[test]
@@ -385,4 +390,10 @@ mod test {
             assert_eq!(&normalized.to_string(), expected);
         }
     }
+
+    #[test]
+    fn test_format_radix_doesnt_panic_with_result_less_than_6_characters() {
+        let hash = format_radix(djb2_hash("/lookup/[domain]/(dns)"), 36);
+        assert!(hash.len() < 6);
+    }
 }