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/device/device.go

@@ -0,0 +1,21 @@
+// Package device abstracts the Lian Li Galahad II LCD hardware. The streamer
+// depends only on the Device interface, so tests can substitute a fake and
+// future hardware can be supported by adding new implementations.
+package device
+
+import (
+	"context"
+	"errors"
+)
+
+// Device sends H.264 frames to a display. Implementations must be safe for
+// sequential use by a single goroutine.
+type Device interface {
+	// WriteFrame transmits one encoded access unit to the display.
+	WriteFrame(ctx context.Context, frame []byte) error
+	// Close releases all hardware resources.
+	Close() error
+}
+
+// ErrNotFound is returned when no matching USB device is present.
+var ErrNotFound = errors.New("device not found")