feat: add QR code functional tests across 41 languages

Native QR generation for each language's ecosystem:
- 27 languages use package manager QR libraries (qrcode, rqrcode, ZXing, etc.)
- 10 languages use C FFI to libqrencode (dlopen, ISO_C_BINDING, @cImport, critcl)
- 2 shell languages use qrencode CLI (native shell paradigm)
- 1 language (Prolog) uses C FFI with CLI fallback

Section 9 added to test-sdk.sh with get_qr_file() mapping and
QR:unsandbox-qr-ok:ROWS pattern validation across the hydra matrix.

test/qr.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+#include <dlfcn.h>
+
+extern "C" {
+    typedef struct { int version; int width; unsigned char *data; } QRcode;
+}
+
+int main() {
+    void *lib = dlopen("libqrencode.so", RTLD_LAZY);
+    if (!lib) { std::cerr << "dlopen: " << dlerror() << std::endl; return 1; }
+
+    auto encode = reinterpret_cast<QRcode*(*)(const char*, int, int, int, int)>(
+        dlsym(lib, "QRcode_encodeString"));
+    auto qfree = reinterpret_cast<void(*)(QRcode*)>(
+        dlsym(lib, "QRcode_free"));
+
+    QRcode *qr = encode("unsandbox-qr-ok", 0, 1, 2, 1);
+    if (!qr) { std::cerr << "encode failed" << std::endl; return 1; }
+
+    std::cout << "QR:unsandbox-qr-ok:ROWS:" << qr->width << std::endl;
+    qfree(qr);
+    dlclose(lib);
+    return 0;
+}