Use gopsutil for cross-platform process detection

Replace pgrep with gopsutil/v4 for pure Go process detection.
Now fully cross-platform (Linux, FreeBSD, macOS, Windows) with
zero external exec calls. Add Taskfile and test fixture.

main.go

@@ -5,12 +5,12 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"regexp"
 	"strings"
 
 	"github.com/go-git/go-git/v6"
+	"github.com/shirou/gopsutil/v4/process"
 	"golang.org/x/sys/unix"
 )
 
@@ -118,10 +118,20 @@ func formatContextInfo(contextSize int, usage *struct {
 }
 
 func getGiteaStatus() string {
-	// Check if gitea process is running using pgrep
-	cmd := exec.Command("pgrep", "-x", "gitea")
-	if err := cmd.Run(); err == nil {
-		return green + "●" + reset
+	// Check if gitea process is running using gopsutil (cross-platform)
+	procs, err := process.Processes()
+	if err != nil {
+		return red + "●" + reset
+	}
+
+	for _, p := range procs {
+		name, err := p.Name()
+		if err != nil {
+			continue
+		}
+		if name == "gitea" {
+			return green + "●" + reset
+		}
 	}
 	return red + "●" + reset
 }