test: prevent virtualenvwrapper temp directory collisions (Fixes #498) (#499)

## Summary

- retain timestamp and process ID uniqueness for virtualenvwrapper test
directories
- add a process-local atomic sequence so parallel tests cannot collide
at coarse clock resolution
- preserve existing explicit cleanup behavior

## Validation

- 20 consecutive `cargo test -p pet-virtualenvwrapper --lib --quiet`
runs
- `cargo test -p pet-virtualenvwrapper --lib`
- `.\scripts\rust-precommit.ps1`

Fixes #498

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: karthiknadig

crates/pet-virtualenvwrapper/src/environments.rs

@@ -59,19 +59,23 @@ mod tests {
     use std::{
         fs,
         path::Path,
+        sync::atomic::{AtomicUsize, Ordering},
         time::{SystemTime, UNIX_EPOCH},
     };
 
     #[cfg(windows)]
     use std::os::windows::fs::symlink_dir;
 
+    static NEXT_TEST_DIR_ID: AtomicUsize = AtomicUsize::new(0);
+
     fn create_test_dir(name: &str) -> PathBuf {
-        let unique = SystemTime::now()
+        let id = NEXT_TEST_DIR_ID.fetch_add(1, Ordering::Relaxed);
+        let timestamp = SystemTime::now()
             .duration_since(UNIX_EPOCH)
             .unwrap()
             .as_nanos();
         let directory = std::env::temp_dir().join(format!(
-            "pet-virtualenvwrapper-{name}-{}-{unique}",
+            "pet-virtualenvwrapper-{name}-{}-{timestamp}-{id}",
             std::process::id()
         ));
         fs::create_dir_all(&directory).unwrap();