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_demo.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+# 复现宿主 + MIPS 版 HTTPS/加密 demo 与 RSA raw 校验。
+# 依赖：先运行 build_mbedtls.sh（产出 out/mbedtls/{host,mipsel}/*.a）。
+#  宿主 = 本机(此工作区为 aarch64)；MIPS = qemu-mipsel 可跑(静态链)。
+. ./libs_common.sh
+
+INC="-I$VENDOR/mbedtls/include -I$VENDOR/jsmn"
+HOST_LIBS="-L$OUT/mbedtls/host -lmbedtls -lmbedx509 -lmbedcrypto"
+MIPS_LIBS="$OUT/mbedtls/mipsel/libmbedtls.a $OUT/mbedtls/mipsel/libmbedx509.a $OUT/mbedtls/mipsel/libmbedcrypto.a"
+
+echo "==> host https_unikey"
+$CC_HOST -O2 $INC demo/https_unikey.c $HOST_LIBS -o demo/https_unikey -lpthread -lm \
+  && echo "  built demo/https_unikey" \
+  && { [ -f /etc/ssl/certs/ca-certificates.crt ] && timeout 45 ./demo/https_unikey | tail -4; }
+
+echo "==> mipsel https_unikey (静态)"
+$CC_MIPS -O2 -static -Wl,--gc-sections $INC demo/https_unikey.c $MIPS_LIBS -o out/https_unikey_mipsel -lpthread -lm \
+  && echo "  built out/https_unikey_mipsel" && size out/https_unikey_mipsel \
+  && timeout 90 qemu-mipsel ./out/https_unikey_mipsel | tail -4