feat(v2): T-309 no startup foreground grab, auto-close popup, rename buttons

- Comment out Gio's startup SetForegroundWindow/SetFocus in the vendored
  os_windows.go (marked SILVER-POSE PATCH; reverts on re-vendor) so the
  window no longer steals foreground on launch. Gio has no option for this.
- The fall confirm popup auto-closes 5s after opening (op.InvalidateCmd
  schedules the redraw even with no live frames); '我已知晓' still closes early.
- Rename save buttons to 保存摄像头参数 / 保存常用检测参数. Cross-compiles for Windows.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

v2/internal/ui/window.go

@@ -115,6 +115,7 @@ type Window struct {
 	latestImage *image.RGBA
 	imageGen    uint64
 	pending     *alert.Record
+	pendingAt   time.Time
 	seenAlerts  map[string]struct{}
 	incoming    []galleryIncoming
 	seenEvents  map[string]struct{}
@@ -335,6 +336,7 @@ func (window *Window) PresentAlert(record alert.Record) {
 	window.seenAlerts[record.Event.EventID] = struct{}{}
 	queued := record
 	window.pending = &queued
+	window.pendingAt = time.Now()
 	window.mu.Unlock()
 	playAlertSound()
 	window.appWindow.Invalidate()
@@ -360,6 +362,7 @@ func (window *Window) layout(gtx layout.Context) layout.Dimensions {
 	frame := window.latestImage
 	gen := window.imageGen
 	pending := window.pending
+	pendingAt := window.pendingAt
 	incoming := window.incoming
 	running := window.running
 	window.incoming = nil
@@ -410,6 +413,17 @@ func (window *Window) layout(gtx layout.Context) layout.Dimensions {
 		window.mu.Unlock()
 		pending = nil
 	}
+	// The confirm popup auto-closes 5 seconds after it opens.
+	if pending != nil {
+		if time.Since(pendingAt) >= 5*time.Second {
+			window.mu.Lock()
+			window.pending = nil
+			window.mu.Unlock()
+			pending = nil
+		} else {
+			gtx.Execute(op.InvalidateCmd{At: pendingAt.Add(5 * time.Second)})
+		}
+	}
 
 	content := func(gtx layout.Context) layout.Dimensions {
 		return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
@@ -701,7 +715,7 @@ func (window *Window) layoutSettings(gtx layout.Context, model ViewModel) layout
 		window.editorRow("传输 (tcp/udp)", &window.editTransport),
 		window.editorRow("连接超时 (秒)", &window.editTimeout),
 		window.checkRow("低延迟", &window.lowLatency),
-		window.buttonRow(&window.saveCamera, "保存摄像头"),
+		window.buttonRow(&window.saveCamera, "保存摄像头参数"),
 	)
 	paramsCard := verticalRows(
 		window.heading("常用检测参数（下次启动生效）"),
@@ -711,7 +725,7 @@ func (window *Window) layoutSettings(gtx layout.Context, model ViewModel) layout
 		window.editorRow("模型置信度", &window.editModelConf),
 		window.checkRow("要求先快速下移", &window.requireRapid),
 		window.checkRow("要求膝踝清晰", &window.requireLower),
-		window.buttonRow(&window.saveParams, "保存参数"),
+		window.buttonRow(&window.saveParams, "保存常用检测参数"),
 		window.labelRow(window.settingsStatus),
 	)
 	depsCard := verticalRows(