Initial commit: Go driver for the Lian Li Galahad II LCD

Streams H.264 to the Galahad II LCD via USB (gousb) with:
- ffmpeg CLI transcoding (no fragile FFmpeg C-ABI bindings)
- pure-Go Annex-B access-unit splitting
- framerate pacing with graceful shutdown and USB reconnect
- TOML config, cobra CLI, structured slog logging, unit tests

internal/cli/root.go

@@ -0,0 +1,66 @@
+// Package cli implements the galahad2lcd command-line interface.
+package cli
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+// Execute runs the CLI and returns the first error encountered. The version
+// is injected by the caller (typically main via -ldflags).
+func Execute(version string) error {
+	root := newRootCmd(version)
+	return root.Execute()
+}
+
+func newRootCmd(version string) *cobra.Command {
+	var verbose bool
+
+	root := &cobra.Command{
+		Use:   "galahad2lcd",
+		Short: "Driver for the Lian Li Galahad II LCD",
+		Long: `galahad2lcd streams H.264 video to the Lian Li Galahad II LCD
+display over USB.`,
+		SilenceUsage:  true,
+		SilenceErrors: true,
+		PersistentPreRun: func(cmd *cobra.Command, _ []string) {
+			level := slog.LevelInfo
+			if verbose {
+				level = slog.LevelDebug
+			}
+			slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: level})))
+		},
+	}
+
+	root.PersistentFlags().BoolVarP(&verbose, "verbose", "v", false, "enable debug logging")
+
+	root.AddCommand(
+		newDaemonCmd(),
+		newSetCmd(),
+		newListCmd(),
+		newVersionCmd(version),
+	)
+	return root
+}
+
+func newVersionCmd(version string) *cobra.Command {
+	return &cobra.Command{
+		Use:   "version",
+		Short: "Print the version and exit",
+		Args:  cobra.NoArgs,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			fmt.Fprintln(cmd.OutOrStdout(), version)
+			return nil
+		},
+	}
+}
+
+// signalContext returns a context cancelled on SIGINT and SIGTERM so that
+// systemctl stop and Ctrl-C both trigger a clean shutdown.
+func signalContext() (context.Context, context.CancelFunc) {
+	return newSignalContext()
+}