Negotiate and decode snapshot-bound canonical model streams

src/app/api/foundry/[...path]/route.ts

@@ -72,6 +72,8 @@ async function handler(
   const project = process.env.NEXT_PUBLIC_FOUNDRY_PROJECT || "endoleap";
   const headers: Record<string, string> = { "Content-Type": asset ? (req.headers.get("content-type") || "application/octet-stream") : "application/json" };
   if (canvas) headers.Accept = "application/vnd.foundry.canvas+json;version=2";
+  const modelStream = canonical && path.endsWith('/canvas/model') && req.method==='GET' && req.headers.get('accept')==='application/vnd.foundry.canvas-model+ndjson;version=1';
+  if(modelStream)headers.Accept='application/vnd.foundry.canvas-model+ndjson;version=1';
   const session = req.cookies.get("foundry_session")?.value;
   if (session) headers.Authorization = "Bearer " + session;
   for (const h of ["x-foundry-code", "x-foundry-verifier", "if-match", "idempotency-key", "x-expected-account", "x-resource-id"]) {
@@ -133,7 +135,7 @@ async function handler(
     // Snapshots contain no login exchange payload. Forward them without buffering
     // and parsing/re-encoding multi-megabyte inline image JSON in the proxy.
     if (canonical || canvas && path.endsWith("/canvas") && req.method === "GET" && upstream.ok) {
-      responseHeaders.set("Content-Type", "application/json; charset=utf-8");
+      responseHeaders.set("Content-Type", modelStream && upstream.ok && upstream.headers.get('content-type')?.startsWith('application/vnd.foundry.canvas-model+ndjson;') ? upstream.headers.get('content-type')! : "application/json; charset=utf-8");
       responseHeaders.set("Server-Timing", `upstream;dur=${(headersReceived - started).toFixed(1)}, proxy_headers;dur=${(performance.now() - headersReceived).toFixed(1)}`);
       return new NextResponse(upstream.body, { status: upstream.status, headers: responseHeaders });
     }