feat: fix flaky generate test and format tunnel.rs

- Fix race condition in generate test temp_dir() by using PID + atomic counter
  instead of nanosecond timestamps that collide under parallel test execution
- Apply cargo fmt to tunnel.rs for consistent formatting

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/generate.rs

@@ -200,12 +200,13 @@ mod tests {
     use crate::redact;
 
     fn temp_dir() -> std::path::PathBuf {
+        // Use process ID + monotonic counter to avoid collisions when tests run in parallel
+        static COUNTER: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
+        let unique = COUNTER.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
         std::env::temp_dir().join(format!(
-            "rustunnel_generate_test_{}",
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap_or_default()
-                .as_nanos()
+            "rustunnel_generate_test_{}_{}",
+            std::process::id(),
+            unique
         ))
     }