Document Python dependency and make integration tests conditional

- Update README.md to mention Python 3 requirement for integration tests
- Make rate limiting test skip gracefully if Python 3 is not available
- Move and rename test helper script to tests/gemini_test_client.py
- Update test to use new script path
- Improve test documentation and error handling

tests/rate_limiting.rs

@@ -2,6 +2,10 @@ use std::process::Command;
 
 #[test]
 fn test_rate_limiting_with_concurrent_requests() {
+    if !python_available() {
+        println!("Skipping rate limiting test: Python 3 not available");
+        return;
+    }
     // Create temp config with max_concurrent_requests = 1
     let temp_dir = std::env::temp_dir();
     let config_path = temp_dir.join("pollux_test_config.toml");
@@ -35,7 +39,7 @@ fn test_rate_limiting_with_concurrent_requests() {
     for _ in 0..5 {
         let handle = std::thread::spawn(|| {
             Command::new("python3")
-                .arg("tmp/test_rate_limit_python.py")
+                .arg("tests/gemini_test_client.py")
                 .arg("--limit")
                 .arg("1")
                 .arg("--host")
@@ -76,4 +80,12 @@ fn test_rate_limiting_with_concurrent_requests() {
     // Verify: 1 success, 4 rate limited
     assert_eq!(success_count, 1);
     assert_eq!(rate_limited_count, 4);
+}
+
+fn python_available() -> bool {
+    std::process::Command::new("python3")
+        .arg("--version")
+        .output()
+        .map(|output| output.status.success())
+        .unwrap_or(false)
 }