Add files via upload

extras/cpp/audio_meta.hpp

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+// extras/cpp — decorative, separate from installer/installer.cpp (the real,
+// functional C++ source). a tiny header-only audio-tag toy, mirroring
+// app/backend/metadata.py in spirit.
+#pragma once
+
+#include <string>
+#include <optional>
+#include <sstream>
+#include <vector>
+
+namespace nexdex {
+
+struct AudioTag {
+    std::string title;
+    std::string artist;
+    std::optional<std::string> album;
+    std::optional<int> year;
+    std::optional<int> trackNumber;
+
+    bool isComplete() const {
+        return !title.empty() && !artist.empty();
+    }
+
+    std::string describe() const {
+        std::ostringstream out;
+        out << artist << " -- " << title;
+        if (album) out << " [" << *album << "]";
+        if (year) out << " (" << *year << ")";
+        if (trackNumber) out << " track #" << *trackNumber;
+        return out.str();
+    }
+};
+
+class AudioTagBuilder {
+public:
+    AudioTagBuilder(std::string title, std::string artist) {
+        tag_.title = std::move(title);
+        tag_.artist = std::move(artist);
+    }
+
+    AudioTagBuilder& album(std::string album) {
+        tag_.album = std::move(album);
+        return *this;
+    }
+
+    AudioTagBuilder& year(int year) {
+        tag_.year = year;
+        return *this;
+    }
+
+    AudioTagBuilder& trackNumber(int n) {
+        tag_.trackNumber = n;
+        return *this;
+    }
+
+    AudioTag build() const {
+        return tag_;
+    }
+
+private:
+    AudioTag tag_;
+};
+
+inline std::vector<std::string> knownExtensions() {
+    return {"mp3", "flac", "wav", "m4a", "alac", "ogg", "opus"};
+}
+
+}  // namespace nexdex