Fix device discovery: include fake devices, size Discover button to text

- Remove FakeDevice filter from GUI discovery so fake mounts/cameras appear
- Size Discover button dynamically to fit "Discovering..." label text

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sebgod

src/TianWen.UI.Gui/Program.cs

@@ -487,7 +487,6 @@ void HandleEquipmentClick(EquipmentHitResult hit)
                         eqState.DiscoveredDevices = [.. dm.RegisteredDeviceTypes
                             .Where(t => t is not DeviceType.Profile and not DeviceType.None)
                             .SelectMany(dm.RegisteredDevices)
-                            .Where(d => d is not TianWen.Lib.Devices.Fake.FakeDevice)
                             .OrderBy(d => d.DeviceType).ThenBy(d => d.DisplayName)];
                     }
                     catch (Exception ex)

src/TianWen.UI.Gui/VkEquipmentTab.cs

@@ -516,9 +516,9 @@ private void RenderDeviceList(
 
             // [Discover] button at the bottom of the list area
             var discoverBtnY = y + h - buttonH - padding;
-            var discoverBtnW = 100f * dpiScale;
-            var discoverBtnX = x + padding;
             var discoverLabel = State.IsDiscovering ? "Discovering..." : "Discover";
+            var discoverBtnW = _renderer.MeasureText(discoverLabel.AsSpan(), fontPath, fontSize).Width + padding * 4f;
+            var discoverBtnX = x + padding;
 
             FillRect(discoverBtnX, discoverBtnY, discoverBtnW, buttonH, CreateButton);
             RegisterClickable(discoverBtnX, discoverBtnY, discoverBtnW, buttonH, new EquipmentHitResult(EquipmentHitType.DiscoverButton));