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/signal.go

@@ -0,0 +1,14 @@
+package cli
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+// newSignalContext returns a context that is cancelled on SIGINT or SIGTERM,
+// so that Ctrl-C and systemctl stop both trigger a clean shutdown.
+func newSignalContext() (context.Context, context.CancelFunc) {
+	return signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+}