Drop EM_ASM_ side-channel; read frame fields from nftMarker directly

The EM_ASM_ block in readNFTMarker mirrored imgBW, imgBWsize, and
F_points_NFT onto a JS-side arfset.frameMalloc global on every load.
Those three values are already returned through the embind nftMarker
value_object (pointer, imgBWsize, nftFeaturePoints), so the side
channel is pure duplication plus an extra wasm->JS crossing.

Remove the EM_ASM_ block and have both src/ARFset.js and the legacy
js/arfset.api.js read directly from the returned struct.

Closes #17

Author: claude

emscripten/ARimageFsetDisplay.cpp

@@ -175,18 +175,6 @@ nftMarker readNFTMarker(int id, std::string datasetPathname) {
 
   arc->surfaceSetCount++;
 
-  EM_ASM_(
-      {
-        if (!arfset["frameMalloc"]) {
-          arfset["frameMalloc"] = ({});
-        }
-        var frameMalloc = arfset["frameMalloc"];
-        frameMalloc["frameIbwpointer"] = $1;
-        frameMalloc["frameimgBWsize"] = $2;
-        frameMalloc["frameFeaturePoints"] = $3
-      },
-      arc->id, arc->imgBW, arc->imgBWsize, arc->F_points_NFT);
-
   nft.nftPoints.reserve(arc->num_F_points_NFT);
   for (int i = 0; i < arc->num_F_points_NFT; i++) {
     nftPoint p;

js/arfset.api.js

@@ -127,11 +127,8 @@ ARfset.prototype.loadNFTMarker = function (markerURL, onSuccess, onError) {
     var self = this;
     if (markerURL) {
       return arfset.readNFTMarker(this.id, markerURL, function (nftMarker) {
-          //console.log(nftMarker);
-          //console.log(nftMarker.nftPoints);
-          var params = arfset.frameMalloc;
-          self.frameIbwpointer = params.frameIbwpointer;
-          self.frameimgBWsize = params.frameimgBWsize;
+          self.frameIbwpointer = nftMarker.pointer;
+          self.frameimgBWsize = nftMarker.imgBWsize;
           var nftEvent = new CustomEvent('nftMarker', {
             detail: {
               numIset: nftMarker.numIset,

src/ARFset.js

@@ -155,9 +155,8 @@ export default class ARFset {
     async loadNFTMarker (urlOrData) {
         let nft = await this.addNFTMarker(this.id, urlOrData)
         .then((nftMarker) => {
-             var params = arfset.frameMalloc;
-              this.frameIbwpointer = params.frameIbwpointer;
-              this.frameimgBWsize = params.frameimgBWsize;
+              this.frameIbwpointer = nftMarker.pointer;
+              this.frameimgBWsize = nftMarker.imgBWsize;
               var nftEvent = new CustomEvent('nftMarker', {
                 detail: {
                   numIset: nftMarker.numIset,
@@ -180,9 +179,8 @@ export default class ARFset {
       async loadNFTMarkerBlob (urlOrData) {
         let nft = await this.addNFTMarkerBlob(this.id, urlOrData)
         .then((nftMarker) => {
-             var params = arfset.frameMalloc;
-              this.frameIbwpointer = params.frameIbwpointer;
-              this.frameimgBWsize = params.frameimgBWsize;
+              this.frameIbwpointer = nftMarker.pointer;
+              this.frameimgBWsize = nftMarker.imgBWsize;
               var nftEvent = new CustomEvent('nftMarker', {
                 detail: {
                   numIset: nftMarker.numIset,