app+csdk+docs: 修正上一轮最近邻2×的退化（颗粒/边沿台阶）——照片改为从160×120单级6×放大（官方ImageViewer同款），实时缓冲与csdk回退为插值2×；实测冷区|dx| 0.76×官方（更平滑），119单测全绿

csdk/tools/mag160c_linux_demo.c

@@ -134,7 +134,12 @@ int main(int argc, char **argv) {
     cfg.cdf_pivot_75 = 1;      /* kept for the PC path */
     cfg.android_lut = 1;
     cfg.fpa_temp_fix = 1699;   /* BasePara2.fpaTempFix of device 160043865 */
-    cfg.upscale_nearest = 1;   /* official Android path has no interpolating 2x stage */
+    /* Keep the interpolating 2x: the nearest variant halves the effective
+       resolution (2-sensor-pixel granules / a coarse staircase on hot-cold edges),
+       which was visible on device.  A display path that consumes gray160 directly
+       needs no intermediate stage at all - that is what the Android app now does
+       for its photos (single 6x step from the sensor grid). */
+    cfg.upscale_nearest = 0;
     cfg.ffc_cb = ffc_cb;
     mag160c_render_t *render = NULL;
     if (mag160c_render_init(&render, &cfg) != MAG160C_OK) {