Release 3.8.2.1: reliability, UI probe/logs, CI, signing gates.

Clear sysproxy on core death; probe+reconnect; subscription prune;
Best ignores soft UDP; Windows tray; Android protocol gate; CI workflows.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/trayhost/tray_stub.go

@@ -0,0 +1,10 @@
+//go:build !windows
+
+package trayhost
+
+// macOS/Linux: no CGO tray in default CGO_ENABLED=0 builds.
+func start(appName string, h Hooks) bool {
+	_ = appName
+	_ = h
+	return false
+}