feat: add Go/Bubble Tea TUI rewrite (apps/tui-go)

Reimplement the TUI in Go using Bubble Tea, replacing the Kotlin/Tamboui
app. Same WebSocket protocol, soft-rounded layout with blue accent theme.

apps/tui-go/main.go

@@ -0,0 +1,31 @@
+// Command tui is the correx terminal UI: a Bubble Tea client that speaks the
+// correx WebSocket protocol to apps/server.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/correx/tui-go/internal/app"
+	"github.com/correx/tui-go/internal/ws"
+)
+
+func main() {
+	host := flag.String("host", "localhost", "server host")
+	port := flag.Int("port", 8080, "server port")
+	flag.Parse()
+
+	client := ws.New(*host, *port)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go client.Run(ctx)
+
+	p := tea.NewProgram(app.NewModel(client), tea.WithAltScreen())
+	if _, err := p.Run(); err != nil {
+		fmt.Fprintln(os.Stderr, "correx tui error:", err)
+		os.Exit(1)
+	}
+}