refactor: restructure codebase to internal/ directory with modular architecture

- Move all source files to internal/{app,backend,config,executor,logger,parser,utils}
- Integrate third-party libraries: zerolog, goccy/go-json, gopsutil, cobra/viper
- Add comprehensive unit tests for utils package (94.3% coverage)
- Add performance benchmarks for string operations
- Fix error display: cleanup warnings no longer pollute Recent Errors
- Add GitHub Actions CI workflow
- Add Makefile for build automation
- Add README documentation

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

codeagent-wrapper/internal/logger/process_check_test.go

@@ -0,0 +1,112 @@
+package logger
+
+import (
+	"math"
+	"os"
+	"os/exec"
+	"runtime"
+	"strconv"
+	"testing"
+	"time"
+)
+
+func TestIsProcessRunning(t *testing.T) {
+	t.Run("boundary values", func(t *testing.T) {
+		if isProcessRunning(0) {
+			t.Fatalf("pid 0 should never be treated as running")
+		}
+		if isProcessRunning(-1) {
+			t.Fatalf("negative pid should never be treated as running")
+		}
+	})
+
+	t.Run("pid out of int32 range", func(t *testing.T) {
+		if strconv.IntSize <= 32 {
+			t.Skip("int cannot represent values above int32 range")
+		}
+
+		pid := int(int64(math.MaxInt32) + 1)
+		if isProcessRunning(pid) {
+			t.Fatalf("expected pid %d (out of int32 range) to be treated as not running", pid)
+		}
+	})
+
+	t.Run("current process", func(t *testing.T) {
+		if !isProcessRunning(os.Getpid()) {
+			t.Fatalf("expected current process (pid=%d) to be running", os.Getpid())
+		}
+	})
+
+	t.Run("fake pid", func(t *testing.T) {
+		const nonexistentPID = 1 << 30
+		if isProcessRunning(nonexistentPID) {
+			t.Fatalf("expected pid %d to be reported as not running", nonexistentPID)
+		}
+	})
+
+	t.Run("terminated process", func(t *testing.T) {
+		pid := exitedProcessPID(t)
+		if isProcessRunning(pid) {
+			t.Fatalf("expected exited child process (pid=%d) to be reported as not running", pid)
+		}
+	})
+}
+
+func exitedProcessPID(t *testing.T) int {
+	t.Helper()
+
+	var cmd *exec.Cmd
+	if runtime.GOOS == "windows" {
+		cmd = exec.Command("cmd", "/c", "exit 0")
+	} else {
+		cmd = exec.Command("sh", "-c", "exit 0")
+	}
+
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("failed to start helper process: %v", err)
+	}
+	pid := cmd.Process.Pid
+
+	if err := cmd.Wait(); err != nil {
+		t.Fatalf("helper process did not exit cleanly: %v", err)
+	}
+
+	time.Sleep(50 * time.Millisecond)
+	return pid
+}
+
+func TestGetProcessStartTimeReadsProcStat(t *testing.T) {
+	start := getProcessStartTime(os.Getpid())
+	if start.IsZero() {
+		t.Fatalf("expected non-zero start time for current process")
+	}
+	if start.After(time.Now().Add(5 * time.Second)) {
+		t.Fatalf("start time is unexpectedly in the future: %v", start)
+	}
+}
+
+func TestGetProcessStartTimeInvalidData(t *testing.T) {
+	if !getProcessStartTime(0).IsZero() {
+		t.Fatalf("expected zero time for pid 0")
+	}
+	if !getProcessStartTime(-1).IsZero() {
+		t.Fatalf("expected zero time for negative pid")
+	}
+	if !getProcessStartTime(1 << 30).IsZero() {
+		t.Fatalf("expected zero time for non-existent pid")
+	}
+	if strconv.IntSize > 32 {
+		pid := int(int64(math.MaxInt32) + 1)
+		if !getProcessStartTime(pid).IsZero() {
+			t.Fatalf("expected zero time for pid %d (out of int32 range)", pid)
+		}
+	}
+}
+
+func TestGetBootTimeParsesBtime(t *testing.T) {
+	t.Skip("legacy boot-time probing removed; start time now uses gopsutil")
+}
+
+func TestGetBootTimeInvalidData(t *testing.T) {
+	t.Skip("legacy boot-time probing removed; start time now uses gopsutil")
+}