fix(selector): safe type assertion, clean up debug logging, add doc comments and 64 tests

Replace bare type assertion in ParallelStrategy with comma-ok check to
prevent panic on non-Node inputs. Downgrade noisy Infof hash-selection
log to Tracef and remove Chinese-language debug output. Add doc comments
to all exported symbols in weighted.go.

selector/setup_test.go

@@ -0,0 +1,14 @@
+package selector
+
+import (
+	"os"
+	"testing"
+
+	corelogger "github.com/go-gost/core/logger"
+	xlogger "github.com/go-gost/x/logger"
+)
+
+func TestMain(m *testing.M) {
+	corelogger.SetDefault(xlogger.Nop())
+	os.Exit(m.Run())
+}