test(signserver): push coverage from 62.9% to 70.3%

Add handlePacket dispatch tests for all switch cases (DSGN, SIGN,
DLTSKEYSIGN, PS4SGN, PS3SGN, VITASGN, WIIUSGN, COGLNK, VITACOGLNK,
DELETE). Add makeSignResponse branch tests covering PSN client PSNID
field, CapLink key/host paths, MezFes minigame switch, non-localhost
remote addr, and PSN token registration. Add startSignCapture
enabled-path tests with temp dir and default output dir.

server/signserver/sys_capture_test.go

@@ -2,6 +2,7 @@ package signserver
 
 import (
 	"net"
+	"os"
 	"testing"
 
 	cfg "erupe-ce/config"
@@ -80,3 +81,76 @@ func TestStartSignCapture_EnabledButSignDisabled(t *testing.T) {
 	}
 	cleanup()
 }
+
+func TestStartSignCapture_EnabledSuccess(t *testing.T) {
+	outputDir := t.TempDir()
+	server := &Server{
+		logger: zap.NewNop(),
+		erupeConfig: &cfg.Config{
+			Host: "127.0.0.1",
+			Sign: cfg.Sign{Port: 53312},
+			Capture: cfg.CaptureOptions{
+				Enabled:     true,
+				CaptureSign: true,
+				OutputDir:   outputDir,
+			},
+		},
+	}
+
+	mc := newMockConn()
+	origConn := network.NewCryptConn(mc, cfg.ZZ, nil)
+	remoteAddr := &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 12345}
+
+	resultConn, cleanup := startSignCapture(server, origConn, remoteAddr)
+	defer cleanup()
+
+	if resultConn == origConn {
+		t.Error("startSignCapture() enabled should return a different (recording) conn")
+	}
+}
+
+func TestStartSignCapture_DefaultOutputDir(t *testing.T) {
+	// Use a temp dir as working directory to avoid polluting the project
+	origDir, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tmpDir := t.TempDir()
+	if err := os.Chdir(tmpDir); err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = os.Chdir(origDir) }()
+
+	server := &Server{
+		logger: zap.NewNop(),
+		erupeConfig: &cfg.Config{
+			Host: "127.0.0.1",
+			Sign: cfg.Sign{Port: 53312},
+			Capture: cfg.CaptureOptions{
+				Enabled:     true,
+				CaptureSign: true,
+				OutputDir:   "", // empty → should default to "captures"
+			},
+		},
+	}
+
+	mc := newMockConn()
+	origConn := network.NewCryptConn(mc, cfg.ZZ, nil)
+	remoteAddr := &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 12345}
+
+	resultConn, cleanup := startSignCapture(server, origConn, remoteAddr)
+	defer cleanup()
+
+	if resultConn == origConn {
+		t.Error("startSignCapture() with default dir should return recording conn")
+	}
+
+	// Verify the "captures" directory was created
+	info, err := os.Stat("captures")
+	if err != nil {
+		t.Fatalf("default 'captures' directory not created: %v", err)
+	}
+	if !info.IsDir() {
+		t.Error("'captures' should be a directory")
+	}
+}