🐛 fix(driver-agent): 修复 Windows 测试连接释放失败

- 优先等待驱动代理自然退出，超时后再执行强制终止
- 进程已退出时忽略 Windows 终止权限竞态，避免连接成功被误判为失败
- 统一可选驱动与 MySQL agent 清理流程并补充回归测试

internal/db/agent_process.go

@@ -0,0 +1,60 @@
+package db
+
+import (
+	"errors"
+	"io"
+	"os/exec"
+	"time"
+)
+
+const agentProcessExitTimeout = 2 * time.Second
+
+func closeAgentProcess(stdin io.Closer, cmd *exec.Cmd) error {
+	if stdin != nil {
+		_ = stdin.Close()
+	}
+	if cmd == nil || cmd.Process == nil {
+		return nil
+	}
+	return waitForAgentExit(cmd.Wait, cmd.Process.Kill, agentProcessExitTimeout)
+}
+
+func waitForAgentExit(wait func() error, kill func() error, timeout time.Duration) error {
+	if wait == nil {
+		return nil
+	}
+	if timeout <= 0 {
+		timeout = agentProcessExitTimeout
+	}
+
+	waitCh := make(chan error, 1)
+	go func() {
+		waitCh <- wait()
+	}()
+
+	timer := time.NewTimer(timeout)
+	defer timer.Stop()
+	select {
+	case <-waitCh:
+		return nil
+	case <-timer.C:
+	}
+
+	var killErr error
+	if kill != nil {
+		killErr = kill()
+	}
+
+	timer.Reset(timeout)
+	select {
+	case <-waitCh:
+		// The process is already reaped. A concurrent Kill can report access
+		// denied on Windows even though cleanup completed successfully.
+		return nil
+	case <-timer.C:
+		if killErr != nil {
+			return killErr
+		}
+		return errors.New("driver agent process did not exit after termination")
+	}
+}

internal/db/agent_process_test.go

@@ -0,0 +1,73 @@
+package db
+
+import (
+	"errors"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestWaitForAgentExitIgnoresKillErrorAfterProcessExit(t *testing.T) {
+	waitStarted := make(chan struct{})
+	processExited := make(chan struct{})
+	killErr := errors.New("TerminateProcess: Access is denied")
+
+	err := waitForAgentExit(
+		func() error {
+			close(waitStarted)
+			<-processExited
+			return nil
+		},
+		func() error {
+			<-waitStarted
+			close(processExited)
+			return killErr
+		},
+		50*time.Millisecond,
+	)
+	if err != nil {
+		t.Fatalf("process exit should make the racing kill error irrelevant, got %v", err)
+	}
+}
+
+func TestWaitForAgentExitWaitsBeforeKilling(t *testing.T) {
+	var killCalled atomic.Bool
+
+	err := waitForAgentExit(
+		func() error { return nil },
+		func() error {
+			killCalled.Store(true)
+			return nil
+		},
+		time.Second,
+	)
+	if err != nil {
+		t.Fatalf("graceful process exit returned error: %v", err)
+	}
+	if killCalled.Load() {
+		t.Fatal("process was killed even though it exited during the graceful wait")
+	}
+}
+
+func TestWaitForAgentExitReturnsKillErrorWhenProcessDoesNotExit(t *testing.T) {
+	waitStarted := make(chan struct{})
+	processExited := make(chan struct{})
+	killErr := errors.New("TerminateProcess: Access is denied")
+
+	err := waitForAgentExit(
+		func() error {
+			close(waitStarted)
+			<-processExited
+			return nil
+		},
+		func() error {
+			<-waitStarted
+			return killErr
+		},
+		20*time.Millisecond,
+	)
+	close(processExited)
+	if !errors.Is(err, killErr) {
+		t.Fatalf("expected kill error when the process never exits, got %v", err)
+	}
+}

internal/db/mysql_agent_impl.go

@@ -176,19 +176,7 @@ func (c *mysqlAgentClient) call(req mysqlAgentRequest, out interface{}, fields *
 func (c *mysqlAgentClient) close() error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	var closeErr error
-	if c.stdin != nil {
-		_ = c.stdin.Close()
-	}
-	if c.cmd != nil && c.cmd.Process != nil {
-		if err := c.cmd.Process.Kill(); err != nil {
-			closeErr = err
-		}
-	}
-	if c.cmd != nil {
-		_ = c.cmd.Wait()
-	}
-	return closeErr
+	return closeAgentProcess(c.stdin, c.cmd)
 }
 
 type MySQLAgentDB struct {

internal/db/optional_driver_agent_impl.go

@@ -416,19 +416,7 @@ func (c *optionalDriverAgentClient) forceTerminate() {
 func (c *optionalDriverAgentClient) close() error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	var closeErr error
-	if c.stdin != nil {
-		_ = c.stdin.Close()
-	}
-	if c.cmd != nil && c.cmd.Process != nil {
-		if err := c.cmd.Process.Kill(); err != nil {
-			closeErr = err
-		}
-	}
-	if c.cmd != nil {
-		_ = c.cmd.Wait()
-	}
-	return closeErr
+	return closeAgentProcess(c.stdin, c.cmd)
 }
 
 type OptionalDriverAgentDB struct {