Fix CPU reporting: MikroTik uses 0x80|pct encoding, add CPU to CSV

- MikroTik encodes CPU as 0x80 | percentage (high bit flag)
- Deserialize: mask with 0x7F and cap at 100
- Serialize: set high bit (0x80 | cpu) to match MikroTik format
- CSV now includes local_cpu_pct and remote_cpu_pct columns
- Both client and server write CPU to CSV

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/full_integration_test.rs

@@ -242,7 +242,7 @@ async fn test_csv_created_client() {
     // Write result like main.rs does
     btest_rs::csv_output::write_result(
         "127.0.0.1", port, "TCP", "receive",
-        2, tx, rx, lost, "none",
+        2, tx, rx, lost, 0, 0, "none",
     );
 
     // Verify CSV exists and has data
@@ -251,7 +251,12 @@ async fn test_csv_created_client() {
     assert!(lines.len() >= 2, "CSV should have header + at least 1 row, got {} lines", lines.len());
     assert!(lines[0].starts_with("timestamp,"), "CSV header missing");
     assert!(lines[1].contains("TCP"), "CSV row should contain protocol");
-    assert!(!lines[1].contains(",0,0,0,"), "CSV should have non-zero bytes");
+    // Check that tx or rx bytes are non-zero (the 7th or 8th CSV field)
+    let fields: Vec<&str> = lines[1].split(',').collect();
+    assert!(fields.len() >= 10, "CSV row should have enough fields");
+    let tx_bytes: u64 = fields[8].parse().unwrap_or(0);
+    let rx_bytes: u64 = fields[9].parse().unwrap_or(0);
+    assert!(tx_bytes > 0 || rx_bytes > 0, "CSV should have non-zero bytes: tx={} rx={}", tx_bytes, rx_bytes);
 
     let _ = std::fs::remove_file(&csv_path);
 }