优化原生结果编码传输与浏览器缓存，记录八路性能基线

原生结果series通过字节索引直传，C端使用Ryu精确回读编码和64 KiB批量写出；网页采用Float64缓存和CSV工作线程，减少结果处理与保存等待。

补充八路AME曲线核查、全流程分阶段计时、独立编码基准和复现工具，固定后续优化采用修正八路及rtol=1e-8。C写出1.1808→0.1638 s，点击到可查看8.0100→6.9756 s。

验证：最终10项编码专项、29项相关后端回归通过；8份原生结果逐位一致，16次网页结果/CSV/刷新恢复通过。前端构建及缓存/CSV专项在本轮结果处理工作中通过。环境、原始大结果与临时构建不纳入Git。

native/runtime/main.c

@@ -1,4 +1,5 @@
 #include "runtime.h"
+#include "json_numbers.h"
 #include <sundials/sundials_config.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -30,7 +31,19 @@ static int probe(void) {
     }
     return 0;
 }
-static int write_result(NativeRun *r, const char *path) {
+static int write_result_index(const char *path, long series_start, long series_end,
+                              long result_bytes, size_t sample_count) {
+    if(series_start<0 || series_end<series_start || result_bytes<series_end) return 0;
+    FILE *index=fopen(path,"wb"); if(!index) return 0;
+    int ok=fprintf(index,"{\"version\":1,\"seriesStart\":%ld,\"seriesEnd\":%ld,"
+                         "\"resultBytes\":%ld,\"sampleCount\":%zu}\n",
+                   series_start,series_end,result_bytes,sample_count)>=0;
+    if(ferror(index)) ok=0;
+    if(fclose(index)) ok=0;
+    return ok;
+}
+static int write_result(NativeRun *r, const char *path, const char *index_path) {
+    if(index_path && !strcmp(path,index_path)) return 0;
     double dy[NSTATES], final[NOUTPUTS];
     int final_ok=model_eval(r->final_time,r->final_state,dy,final);
     size_t length=r->count*NOUTPUTS;
@@ -53,30 +66,48 @@ static int write_result(NativeRun *r, const char *path) {
             r->options.bdf?"BDF":"RK45",r->options.bdf?"CVODE":"Dormand-Prince 5(4)",SUNDIALS_VERSION,
             r->final_time,r->solve_seconds,r->solve_cpu_seconds,r->nfev,r->accepted,r->rejected,
             r->events,r->starts,r->njev,r->nlu,r->max_accepted_step);
+    /* Binary-mode positions delimit the complete series object, including
+       both braces. The optional index avoids scanning or parsing its values. */
+    long series_start=-1,series_end=-1,result_bytes=-1;
+    if(index_path) {
+        series_start=ftell(f);
+        if(series_start>0) series_start--; else series_start=-1;
+    }
+    int output_ok=1;
     if (r->count) {
-        fprintf(f,"\"time\":[");
-        for (size_t i=0;i<r->count;i++) fprintf(f,"%s%.17g",i?",":"",r->times[i]);
-        fputc(']',f);
-        for (int j=0;j<NOUTPUTS;j++) {
-            fputc(',',f); json_string(f,model_output_keys[j]); fprintf(f,":[");
-            for (size_t i=0;i<r->count;i++) fprintf(f,"%s%.17g",i?",":"",values[i*NOUTPUTS+j]);
-            fputc(']',f);
+        fprintf(f,"\"time\":");
+        output_ok=native_json_write_array(f,r->times,r->count,1);
+        for (int j=0;j<NOUTPUTS && output_ok;j++) {
+            fputc(',',f); json_string(f,model_output_keys[j]); fputc(':',f);
+            output_ok=native_json_write_array(f,values+j,r->count,NOUTPUTS);
         }
     }
-    fprintf(f,"},\"final\":{");
-    if (final_ok) for (int j=0;j<NOUTPUTS;j++) {
+    fputc('}',f);
+    if(index_path) series_end=ftell(f);
+    fprintf(f,",\"final\":{");
+    if (final_ok) for (int j=0;j<NOUTPUTS && output_ok;j++) {
         if (j) fputc(',',f);
-        json_string(f,model_output_keys[j]); fprintf(f,":%.17g",final[j]);
+        json_string(f,model_output_keys[j]); fputc(':',f);
+        output_ok=native_json_write_number(f,final[j]);
     }
-    fprintf(f,"},\"finalState\":"); vector(f,r->final_state,NSTATES);
-    fprintf(f,"}\n"); int ok=!ferror(f); if (fclose(f)) ok=0;
+    fprintf(f,"},\"finalState\":");
+    if (output_ok) output_ok=native_json_write_array(f,r->final_state,NSTATES,1);
+    fprintf(f,"}\n"); int ok=output_ok && !ferror(f);
+    if(index_path) {
+        result_bytes=ftell(f);
+        if(series_start<0 || series_end<0 || result_bytes<0) ok=0;
+    }
+    if (fclose(f)) ok=0;
+    /* Publish the index only after the complete result was successfully
+       flushed and closed. An index I/O failure is a failed result write. */
+    if(ok && index_path) ok=write_result_index(index_path,series_start,series_end,result_bytes,r->count);
     free(values); return ok;
 }
 
 int main(int argc, char **argv) {
     NativeRun r={0};
     r.options=(NativeOptions){0,10,.02,.001,1e-6,300,0,1,NULL};
-    const char *output="result.json";
+    const char *output="result.json", *index_path=NULL;
     for (int i=1;i<argc;i++) {
         const char *arg=argv[i];
         if (!strcmp(arg,"--probe")) return probe();
@@ -88,6 +119,7 @@ int main(int argc, char **argv) {
         if (i+1==argc) return 64;
         const char *value=argv[++i];
         if (!strcmp(arg,"--output")) output=value;
+        else if (!strcmp(arg,"--result-index")) index_path=value;
         else if (!strcmp(arg,"--cancel-file")) r.options.cancel_path=value;
         else if (!strcmp(arg,"--method")) {
             if (strcmp(value,"RK45") && strcmp(value,"BDF")) return 64;
@@ -113,7 +145,7 @@ int main(int argc, char **argv) {
         ((r.options.stop-r.options.start)/r.options.sample_step>1000000 ||
          ((r.options.stop-r.options.start)/r.options.sample_step+1024)*(NSTATES+NOUTPUTS)*sizeof(double)>268435456)) return 64;
     native_solve(&r);
-    int saved=write_result(&r,output);
+    int saved=write_result(&r,output,index_path);
     int code=saved?(r.status==2?2:0):3;
     native_run_free(&r); return code;
 }