feat(ncm): 网易云技术栈预研+构建验证 (agent-200) — 选型: mbedtls3.6.2裁剪(TLS+AES+MD5+RSA raw+Base64,~388KB)/jsmn(2.2KB)/qrcodegen(10.8KB)/minimp3(37.4KB), 合计~438KB; HTTPS unikey 全链路宿主+qemu-mipsel 实测通过; RSA raw 与 Python pow 逐字节一致; MP3 解码非瓶颈

vendor源码+out产物不入库(126MB, gitignore; 版本/许可/裁剪见 VENDOR_NOTES.md, build_*.sh 可复现)

patch_v2/ncm_app/build_qrcodegen.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+# qrcodegen (nayuki QR-Code-generator, c/qrcodegen.c) — 静态编译 mipsel。许可 MIT。
+. ./libs_common.sh
+SRC="$VENDOR/qrcodegen/c/qrcodegen.c"
+D="$OUT/qrcodegen/mipsel"; mkdir -p "$D"
+$CC_MIPS -Os -I"$VENDOR/qrcodegen/c" -fno-stack-protector -c "$SRC" -o "$D/qrcodegen.o" || exit 1
+$AR_MIPS rcs "$D/libqrcodegen.a" "$D/qrcodegen.o"
+echo "qrcodegen (mipsel):"
+measure_archive "$D/libqrcodegen.a"