Further fixes; improve error handling

ui/ops.js

@@ -4,29 +4,31 @@ import initModule from '../libapi.mjs';
 
 const ModulePromise = initModule();
 
+export function rethrowIfCritical(err) {
+  // If it's precisely Error, it's a custom error; anything else - SyntaxError,
+  // WebAssembly.RuntimeError, TypeError, etc. - is treated as critical here.
+  if (err.constructor !== Error) {
+    throw err;
+  }
+}
+
 export async function connect() {
   const Module = await ModulePromise;
 
   let context = await new Module.Context();
   let supportedOps = await context.supportedOps();
 
+  /** @type {Promise<unknown>} */
   let queue = Promise.resolve();
 
   /** Schedules an exclusive async operation on the global context.
-   * @template T
+   * @template T,T2
    * @param {(ctx: Context) => Promise<T>} op
    * @returns {Promise<T>}
    */
   function schedule(op) {
     let res = queue.then(() => op(context));
-
-    // Queue should ignore result values as well as errors from singular ops.
-    queue = res.then(
-      () => {},
-      () => {}
-    );
-
-    // Result should contain the unwrapped value or error.
+    queue = res.catch(rethrowIfCritical);
     return res;
   }