Fix SpotBugs DM_DEFAULT_ENCODING: Add UTF-8 charset to InputStreamReader

Co-authored-by: brunoborges <129743+brunoborges@users.noreply.github.com>

Author: Copilot

src/main/java/com/github/copilot/sdk/CopilotClient.java

@@ -10,6 +10,7 @@
 import java.io.InputStreamReader;
 import java.net.Socket;
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -1014,7 +1015,8 @@ private ProcessInfo startCliServer() throws IOException, InterruptedException {
 
         // Forward stderr to logger in background
         Thread stderrThread = new Thread(() -> {
-            try (BufferedReader reader = new BufferedReader(new InputStreamReader(process.getErrorStream()))) {
+            try (BufferedReader reader = new BufferedReader(
+                    new InputStreamReader(process.getErrorStream(), StandardCharsets.UTF_8))) {
                 String line;
                 while ((line = reader.readLine()) != null) {
                     LOG.fine("[CLI] " + line);
@@ -1029,7 +1031,8 @@ private ProcessInfo startCliServer() throws IOException, InterruptedException {
         Integer detectedPort = null;
         if (!options.isUseStdio()) {
             // Wait for port announcement
-            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
+            BufferedReader reader = new BufferedReader(
+                    new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_8));
             Pattern portPattern = Pattern.compile("listening on port (\\d+)", Pattern.CASE_INSENSITIVE);
             long deadline = System.currentTimeMillis() + 30000;