fix(exec): 同步 3.0.x UTF-8 解码修复（Jackson 2 适配）

Author: loong10k

src/main/java/io/github/easy4j/kimi/cli/KimiCliExecutor.java

@@ -168,8 +168,10 @@ private KimiCliResult runProcess(String stdin, String... args) {
         long startNanos = System.nanoTime();
         try {
             int exitCode = executor.execute(cmd);
-            String out = stdout.toString().trim();
-            String err = stderr.toString().trim();
+            // The CLI emits UTF-8; decoding with the platform default charset
+            // corrupts non-ASCII output on C-locale environments.
+            String out = stdout.toString(StandardCharsets.UTF_8).trim();
+            String err = stderr.toString(StandardCharsets.UTF_8).trim();
             log.debug("kimi CLI executed: exitCode={}, stdout.len={}", exitCode, out.length());
             if (watchdog.killedProcess()) {
                 return new KimiCliResult(-1, out, "kimi CLI timed out after " + timeoutMs + " ms\n" + err);
@@ -182,8 +184,8 @@ private KimiCliResult runProcess(String stdin, String... args) {
             // with the real exit code instead of discarding the output. The
             // deadline check makes the timeout verdict race-free even when
             // {@code watchdog.killedProcess()} has not observed the kill yet.
-            String out = stdout.toString().trim();
-            String err = stderr.toString().trim();
+            String out = stdout.toString(StandardCharsets.UTF_8).trim();
+            String err = stderr.toString(StandardCharsets.UTF_8).trim();
             boolean timedOut = watchdog.killedProcess()
                     || System.nanoTime() - startNanos >= timeoutMs * 1_000_000L;
             if (timedOut) {

src/test/java/io/github/easy4j/kimi/cli/KimiCliExecutorTest.java

@@ -88,6 +88,17 @@ void shouldReturnIoExceptionMessageWhenExecutableMissing() {
         assertTrue(result.getStderr() != null && !result.getStderr().isEmpty());
     }
 
+    @Test
+    void shouldDecodeUtf8OutputRegardlessOfPlatformCharset() {
+        // POSIX printf octal escapes emit 你好 as raw UTF-8 bytes; with a
+        // platform-default-charset decode this corrupts on C-locale JVMs.
+        KimiCliExecutor executor = new KimiCliExecutor(configFor("/bin/sh"));
+
+        KimiCliResult result = executor.execute("-c", "printf '\\344\\275\\240\\345\\245\\275'");
+
+        assertEquals("你好", result.getStdout());
+    }
+
     @Test
     void shouldIgnoreNullArguments() {
         KimiCliExecutor executor = new KimiCliExecutor(configFor(ECHO));