fix: restore code queue task submission

- catch async route rejections before Bun fallback HTML\n- return structured JSON for missing reference task ids\n- harden frontend direct proxy JSON handling

src/components/frontend/src/index.ts

@@ -707,6 +707,7 @@ async function proxyCodeQueueDirect(req: Request, url: URL): Promise<Response> {
   }
   const overviewCacheKey = `${suffix}${url.search}`;
   const canUseOverviewCache = req.method === "GET" && suffix === "/api/tasks/overview";
+  const expectsJsonResponse = suffix === "/health" || suffix.startsWith("/api/");
   if (req.method !== "GET" && req.method !== "HEAD") invalidateCodeQueueOverviewCache();
   if (canUseOverviewCache) {
     const cached = cachedCodeQueueOverview(overviewCacheKey);
@@ -736,8 +737,28 @@ async function proxyCodeQueueDirect(req: Request, url: URL): Promise<Response> {
     const isJsonResponse = (upstreamContentType ?? "").toLowerCase().includes("json");
     let parsedJson: unknown = null;
     let jsonText = "";
-    if (canUseOverviewCache && upstream.ok && isJsonResponse) {
+    if (expectsJsonResponse) {
       jsonText = new TextDecoder().decode(upstreamBody);
+      if (!isJsonResponse) {
+        logger("warn", "code_queue_direct_proxy_non_json", {
+          path: suffix,
+          upstreamUrl: upstreamUrl.toString(),
+          status: upstream.status,
+          contentType: upstreamContentType,
+          bodyBytes: upstreamBody.byteLength,
+          preview: safePreview(jsonText),
+        });
+        return jsonResponse({
+          ok: false,
+          error: {
+            message: "code-queue upstream returned non-JSON response",
+            status: upstream.status,
+            contentType: upstreamContentType,
+            bodyBytes: upstreamBody.byteLength,
+            preview: safePreview(jsonText),
+          },
+        }, 502);
+      }
       try {
         parsedJson = jsonText ? JSON.parse(jsonText) as unknown : null;
       } catch (error) {
@@ -757,14 +778,15 @@ async function proxyCodeQueueDirect(req: Request, url: URL): Promise<Response> {
             detail,
             status: upstream.status,
             bodyBytes: upstreamBody.byteLength,
+            contentType: upstreamContentType,
             preview: safePreview(jsonText),
           },
         }, 502);
       }
     }
-    if (canUseOverviewCache && upstream.ok && isJsonResponse) {
+    if (expectsJsonResponse) {
       const text = jsonText;
-      if (typeof parsedJson === "object" && parsedJson !== null) {
+      if (canUseOverviewCache && upstream.ok && typeof parsedJson === "object" && parsedJson !== null) {
         codeQueueOverviewCache.set(codeQueueOverviewCacheKey(overviewCacheKey), { at: Date.now(), payload: parsedJson as JsonValue, text });
       }
       return new Response(text, { status: upstream.status, headers: responseHeaders });