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/list.go

@@ -0,0 +1,57 @@
+package device
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/google/gousb"
+)
+
+// Info describes a USB device for the diagnostics listing.
+type Info struct {
+	VendorID     int
+	ProductID    int
+	Manufacturer string
+	Product      string
+	Serial       string
+	Bus          int
+	Address      int
+	IsLCD        bool
+}
+
+// ListDevices enumerates all USB devices visible to libusb. Descriptor
+// strings are best-effort: reading them requires device access, which is
+// why failures are ignored.
+func ListDevices(ctx context.Context) ([]Info, error) {
+	gctx := gousb.NewContext()
+	defer gctx.Close()
+
+	devs, err := gctx.OpenDevices(func(*gousb.DeviceDesc) bool { return true })
+	if err != nil && len(devs) == 0 {
+		return nil, fmt.Errorf("enumerate USB devices (run as root or install the udev rule): %w", err)
+	}
+	defer func() {
+		for _, d := range devs {
+			_ = d.Close()
+		}
+	}()
+
+	infos := make([]Info, 0, len(devs))
+	for _, d := range devs {
+		info := Info{
+			VendorID:  int(d.Desc.Vendor),
+			ProductID: int(d.Desc.Product),
+			Bus:       d.Desc.Bus,
+			Address:   d.Desc.Address,
+			IsLCD:     d.Desc.Vendor == gousb.ID(0x0416) && d.Desc.Product == gousb.ID(0x7395),
+		}
+		if info.IsLCD {
+			// Only read strings for the device we care about.
+			info.Manufacturer, _ = d.Manufacturer()
+			info.Product, _ = d.Product()
+			info.Serial, _ = d.SerialNumber()
+		}
+		infos = append(infos, info)
+	}
+	return infos, err
+}