feat(classifier): Add JSON label map support, fix encapsulation

- Rewrite LoadLabelMap to support both JSON object format and legacy line format
- Fix CMakeLists.txt test command to use existing WAV file path
- Move WavFileSource::parse_wav_header and resample_if_needed to private section
- Verify JSON label_map works: demo_offline correctly loads and classifies
- All tests pass: test_core_lib 6/6, demo_offline 20/20

src/drone-software/src/acoustic/CMakeLists.txt

@@ -208,7 +208,7 @@ if(BUILD_TESTS)
         endif()
         add_test(NAME classifier_cpp COMMAND test_classifier_cpp
                  --model ${CMAKE_CURRENT_SOURCE_DIR}/models/gunshot_classifier.onnx
-                 --wav ${CMAKE_CURRENT_SOURCE_DIR}/dataset/binary/train/ambient/drone_noise_simulated.wav)
+                 --wav ${CMAKE_CURRENT_SOURCE_DIR}/dataset/binary/val/ambient/drone_noise_val_000.wav)
     endif()
 endif()
 

src/drone-software/src/acoustic/include/acoustic_analyzer/io/wav_file_source.h

@@ -20,8 +20,6 @@ public:
     ~WavFileSource();
 
     bool open();
-    bool parse_wav_header();
-    void resample_if_needed(std::vector<float>& mono, int src_rate, int dst_rate);
     std::size_t read(std::vector<std::vector<float>>& out, std::size_t max_samples);
     void close();
 
@@ -32,6 +30,8 @@ public:
     bool is_open() const { return fp_ != nullptr; }
 
 private:
+    bool parse_wav_header();
+    void resample_if_needed(std::vector<float>& mono, int src_rate, int dst_rate);
     std::string path_;
     int target_sample_rate_;
     std::FILE* fp_;

src/drone-software/src/acoustic/src/core/gunshot_classifier.cpp

@@ -33,32 +33,67 @@ struct GunshotClassifier::Impl {
     bool LoadLabelMap(const std::string& path) {
         std::ifstream f(path);
         if (!f) return false;
-        std::string line;
+        std::string content((std::istreambuf_iterator<char>(f)),
+                             std::istreambuf_iterator<char>());
         labels.clear();
-        while (std::getline(f, line)) {
-            // Parse "index: label" format
-            size_t pos = line.find(':');
-            if (pos == std::string::npos) continue;
-            int idx = 0;
-            try {
-                idx = std::stoi(line.substr(0, pos));
-            } catch (...) {
-                continue;
-            }
-            std::string label = line.substr(pos + 1);
-            // trim whitespace
-            size_t start = label.find_first_not_of(" \t\r\n");
-            size_t end = label.find_last_not_of(" \t\r\n");
-            if (start != std::string::npos && end != std::string::npos) {
-                label = label.substr(start, end - start + 1);
-            } else {
-                label.clear();
+
+        // Try simple JSON object format: {"0": "ambient", "1": "threat"}
+        if (content.find('{') != std::string::npos) {
+            size_t pos = 0;
+            while ((pos = content.find('"', pos)) != std::string::npos) {
+                size_t key_start = pos + 1;
+                size_t key_end = content.find('"', key_start);
+                if (key_end == std::string::npos) break;
+                std::string key = content.substr(key_start, key_end - key_start);
+                int idx = -1;
+                try { idx = std::stoi(key); } catch (...) {}
+
+                size_t colon = content.find(':', key_end);
+                if (colon == std::string::npos) break;
+                size_t val_quote = content.find('"', colon);
+                if (val_quote == std::string::npos) break;
+                size_t val_end = content.find('"', val_quote + 1);
+                if (val_end == std::string::npos) break;
+                std::string label = content.substr(val_quote + 1, val_end - val_quote - 1);
+
+                if (idx >= 0) {
+                    if (idx >= static_cast<int>(labels.size())) labels.resize(idx + 1);
+                    labels[idx] = label;
+                }
+                pos = val_end + 1;
             }
-            if (idx >= static_cast<int>(labels.size())) {
-                labels.resize(idx + 1);
+        } else {
+            // Fallback: "index: label" line format
+            size_t line_start = 0;
+            while (line_start < content.size()) {
+                size_t line_end = content.find('\n', line_start);
+                if (line_end == std::string::npos) line_end = content.size();
+                std::string line = content.substr(line_start, line_end - line_start);
+                line_start = line_end + 1;
+
+                std::size_t pos = line.find(':');
+                if (pos == std::string::npos) continue;
+                int idx = 0;
+                try {
+                    idx = std::stoi(line.substr(0, pos));
+                } catch (...) {
+                    continue;
+                }
+                std::string label = line.substr(pos + 1);
+                std::size_t start = label.find_first_not_of(" \t\r\n");
+                std::size_t end = label.find_last_not_of(" \t\r\n");
+                if (start != std::string::npos && end != std::string::npos) {
+                    label = label.substr(start, end - start + 1);
+                } else {
+                    label.clear();
+                }
+                if (idx >= static_cast<int>(labels.size())) {
+                    labels.resize(idx + 1);
+                }
+                labels[idx] = label;
             }
-            labels[idx] = label;
         }
+
         // Remove empty entries and compact
         std::vector<std::string> cleaned;
         for (const auto& l : labels) {