Update pool_block verify test for Salvium

- Add 200-block test data extracted from live cache

tests/extract_cache.cpp

@@ -0,0 +1,40 @@
+#include <fstream>
+#include <iostream>
+#include <vector>
+#include <cstdint>
+
+static constexpr uint32_t BLOCK_SIZE = 96 * 1024;
+
+int main(int argc, char* argv[]) {
+    if (argc != 4) {
+        std::cerr << "Usage: " << argv[0] << " <cache_file> <output> <num_blocks>\n";
+        return 1;
+    }
+    
+    std::ifstream in(argv[1], std::ios::binary);
+    std::ofstream out(argv[2], std::ios::binary);
+    int max_blocks = std::stoi(argv[3]);
+    
+    std::vector<uint8_t> slot(BLOCK_SIZE);
+    int blocks_written = 0;
+    
+    while (in && blocks_written < max_blocks) {
+        // Read 96KB slot
+        in.read(reinterpret_cast<char*>(slot.data()), BLOCK_SIZE);
+        if (!in) break;
+        
+        // Read size from first 4 bytes
+        uint32_t size = *reinterpret_cast<uint32_t*>(slot.data());
+        
+        // Skip empty slots
+        if (size == 0 || size > BLOCK_SIZE - 4) continue;
+        
+        // Write: size + data
+        out.write(reinterpret_cast<char*>(&size), sizeof(size));
+        out.write(reinterpret_cast<char*>(slot.data() + 4), size);
+        blocks_written++;
+    }
+    
+    std::cout << "Extracted " << blocks_written << " blocks\n";
+    return 0;
+}