Robustness for the USB connection.

ant: replace usb.GetDevice with direct gousb usage

Remove dependency on antgo/driver/usb to fix libusb context leaks on
device-not-found errors. The previous code called usb.GetDevice which
creates a gousb.Context via libusb_init but leaks it on every error
path (device not found, interface claim failure, etc.). Calling
ListenForTrainer repeatedly (e.g. starting with no dongle and plugging
it in later) triggered a libusb assertion in pthread_key_create because
the leaked contexts were never torn down.

Replace with direct gousb calls in ListenForTrainer, managing the
gousb.Context lifecycle explicitly. Cleanup is ordered correctly on
all paths: release interface, close device, close context, cancel
the ANT message goroutine context.

Also convert panics to returned errors for graceful retry.

cmd/bridge/ant.go

@@ -1,16 +1,25 @@
 package main
 
 import (
+	"bufio"
 	"context"
+	"fmt"
 	"io"
 	"time"
 
 	"github.com/google/gousb"
 	"github.com/half2me/antgo/ant"
 	"github.com/half2me/antgo/device"
-	"github.com/half2me/antgo/driver/usb"
 )
 
+type antUSB struct {
+	in  *bufio.Reader
+	out *gousb.OutEndpoint
+}
+
+func (d *antUSB) Read(p []byte) (int, error)  { return d.in.Read(p) }
+func (d *antUSB) Write(p []byte) (int, error) { return d.out.Write(p) }
+
 const (
 	antDataPageMask         = 0x7F // Mask for data page number (7 bits, clears toggle bit)
 	antDataPageCyclingPower = 0x10 // Data page 16 = Cycling Power Feature page
@@ -33,21 +42,44 @@ func resetAndWait(drv io.ReadWriter) error {
 }
 
 func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
-	events chan<- Event) {
+	events chan<- Event) error {
 
-	drv, err := usb.GetDevice(gousb.ID(vendorId), gousb.ID(productId))
+	gctx := gousb.NewContext()
+	defer gctx.Close()
+
+	dev, err := gctx.OpenDeviceWithVIDPID(gousb.ID(vendorId), gousb.ID(productId))
 	if err != nil {
-		panic(err)
+		return fmt.Errorf("ant: open device: %w", err)
 	}
-	defer drv.Close()
+	if dev == nil {
+		return fmt.Errorf("ant: device not found (0x%04x:0x%04x)", vendorId, productId)
+	}
+	defer dev.Close()
+
+	intf, done, err := dev.DefaultInterface()
+	if err != nil {
+		return fmt.Errorf("ant: claim interface: %w", err)
+	}
+	defer done()
+
+	out, err := intf.OutEndpoint(1)
+	if err != nil {
+		return fmt.Errorf("ant: open out endpoint: %w", err)
+	}
+	inp, err := intf.InEndpoint(1)
+	if err != nil {
+		return fmt.Errorf("ant: open in endpoint: %w", err)
+	}
+
+	drv := &antUSB{in: bufio.NewReader(inp), out: out}
 
 	logMsg("ant: device opened")
 
 	if err := resetAndWait(drv); err != nil {
-		panic(err)
+		return err
 	}
 	if err := device.StartRxScanModeWait(drv); err != nil {
-		panic(err)
+		return err
 	}
 	logMsg("ant: scan mode started")
 
@@ -92,7 +124,7 @@ func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
 			}
 		case <-time.After(10 * time.Second):
 			logMsg("ant: no more messages arrived, restarting")
-			return
+			return nil
 		}
 	}
 }

cmd/bridge/cli.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
+	"time"
 
 	"github.com/spf13/cobra"
 )
@@ -83,7 +84,10 @@ This allows these trainers to be used with modern devices that don't support ANT
 			events := make(chan Event, 1)
 			go func() {
 				for {
-					ListenForTrainer(uint16(c.vendorID), uint16(c.productID), c.deviceNumber, events)
+					if err := ListenForTrainer(uint16(c.vendorID), uint16(c.productID), c.deviceNumber, events); err != nil {
+						logPrintf("ant: listener error: %v, retry in 10 seconds\n", err)
+						time.Sleep(10 * time.Second)
+					}
 				}
 			}()
 			ExposeBluetooth(events)