fix: ignore Python install manager target files (Fixes #483) (#484)

## Summary

- require Windows Python executable matches to end at the `.exe` suffix
- exclude Python Install Manager `.__target__` metadata files from
discovery
- add regression coverage for unversioned and versioned target files

## Validation

- `cargo test -p pet-python-utils executable::tests::is_`
- `.\scripts\rust-precommit.ps1`

Fixes #483

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

Author: karthiknadig

crates/pet-python-utils/src/executable.rs

@@ -12,7 +12,7 @@ use std::{
 
 lazy_static! {
     static ref WINDOWS_EXE: Regex =
-        Regex::new(r"python(\d+\.?)*.exe").expect("error parsing Windows executable regex");
+        Regex::new(r"python(\d+\.?)*\.exe$").expect("error parsing Windows executable regex");
     static ref UNIX_EXE: Regex =
         Regex::new(r"python(\d+\.?)*$").expect("error parsing Unix executable regex");
 }
@@ -342,6 +342,18 @@ mod tests {
         assert!(!is_python_executable_name(
             PathBuf::from("pythonw3.exe").as_path()
         ));
+        #[cfg(windows)]
+        assert!(!is_python_executable_name(
+            PathBuf::from("python.exe.__target__").as_path()
+        ));
+        #[cfg(windows)]
+        assert!(!is_python_executable_name(
+            PathBuf::from("python3.exe.__target__").as_path()
+        ));
+        #[cfg(windows)]
+        assert!(!is_python_executable_name(
+            PathBuf::from("python3.12.exe.__target__").as_path()
+        ));
     }
 
     #[test]