refactor: move all app code to internal/termapp and entry to cmd/

Consolidate remaining package main files into internal/termapp for
clean separation: cmd/serialterminal/ is the sole entry point.
Update .goreleaser.yaml to build from ./cmd/serialterminal.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/termapp/config_test.go

@@ -0,0 +1,82 @@
+package termapp
+
+import (
+	"path/filepath"
+	"testing"
+
+	appconfig "github.com/jixishi/SerialTerminalForWindowsTerminal/internal/config"
+	"github.com/jixishi/SerialTerminalForWindowsTerminal/pkg/forward"
+)
+
+func TestForwardModeNetworkAndString(t *testing.T) {
+	tests := []struct {
+		mode    forward.Mode
+		network string
+		name    string
+	}{
+		{mode: forward.None, network: "", name: "none"},
+		{mode: forward.TCP, network: "tcp", name: "tcp"},
+		{mode: forward.UDP, network: "udp", name: "udp"},
+	}
+
+	for _, tt := range tests {
+		if got := tt.mode.Network(); got != tt.network {
+			t.Fatalf("Network() mode=%v got=%q want=%q", tt.mode, got, tt.network)
+		}
+		if got := tt.mode.String(); got != tt.name {
+			t.Fatalf("String() mode=%v got=%q want=%q", tt.mode, got, tt.name)
+		}
+	}
+}
+
+func TestParseForwardMode(t *testing.T) {
+	tests := []struct {
+		input string
+		mode  forward.Mode
+		ok    bool
+	}{
+		{input: "tcp", mode: forward.TCP, ok: true},
+		{input: "TCP-C", mode: forward.TCP, ok: true},
+		{input: "1", mode: forward.TCP, ok: true},
+		{input: "udp", mode: forward.UDP, ok: true},
+		{input: " 2 ", mode: forward.UDP, ok: true},
+		{input: "unknown", mode: forward.None, ok: false},
+		{input: "", mode: forward.None, ok: false},
+	}
+
+	for _, tt := range tests {
+		got, ok := forward.ParseMode(tt.input)
+		if ok != tt.ok || got != tt.mode {
+			t.Fatalf("forward.ParseMode(%q) got=(%v,%v) want=(%v,%v)", tt.input, got, ok, tt.mode, tt.ok)
+		}
+	}
+}
+
+func TestOpenLogFile(t *testing.T) {
+	old := *cfg
+	defer func() { *cfg = old }()
+
+	*cfg = Config{
+		EnableLog:   true,
+		PortName:    "COM1",
+		LogFilePath: filepath.Join(t.TempDir(), "%s-%s.log"),
+	}
+
+	f, err := appconfig.OpenLogFile(cfg)
+	if err != nil {
+		t.Fatalf("openLogFile() unexpected error: %v", err)
+	}
+	if f == nil {
+		t.Fatalf("openLogFile() got nil file when enableLog=true")
+	}
+	_ = f.Close()
+
+	cfg.EnableLog = false
+	f, err = appconfig.OpenLogFile(cfg)
+	if err != nil {
+		t.Fatalf("openLogFile() unexpected error with enableLog=false: %v", err)
+	}
+	if f != nil {
+		t.Fatalf("openLogFile() expected nil file when enableLog=false")
+	}
+}