v2 rebuild: GDI+ single-surface UI, self-calibrating progress, compact push-to-talk, GGML+Whisper integration

src/text_util.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <string>
+
+inline std::wstring append_transcript(const std::wstring& cur, const std::wstring& add) {
+    if (add.empty()) return cur;
+    if (cur.empty()) return add;
+    return cur + L" " + add;
+}