examples(wasm): add a browser parallel-assets demo via Web Workers

Close the final "parallel assets" cell of the cross-language matrix for
WASM.

* examples/wasm/parallel_assets.html — generates a synthetic
  `(assets, bars)` panel deterministically (the LCG matches the Node
  and Rust siblings so timings are directly comparable), runs the
  serial baseline on the main thread, then dispatches the same workload
  to a pool of module Workers and reports the speedup. The render is
  three cards (serial / parallel / speedup) plus a sanity-check line
  asserting per-asset agreement between the two paths.
* examples/wasm/parallel_worker.js — companion module worker that
  loads its own copy of the WebAssembly module via `init()` and
  processes whichever slice of the panel its parent dispatches.

Modern browsers ship module-worker support (`new Worker(url, {
type: "module" })`) which lets every worker do `import init, { SMA, RSI
} from "../../bindings/wasm/pkg/wickra_wasm.js"` without bundler
glue. The inline page module and the worker module both syntax-check
cleanly under `node --check`.

examples/wasm/parallel_worker.js

@@ -0,0 +1,27 @@
+// Module worker for `examples/wasm/parallel_assets.html`. Each worker loads
+// its own copy of the WebAssembly module, then processes the slice of the
+// (assets, bars) panel its parent dispatches via `postMessage` and sends
+// the per-asset "last non-null indicator value" back.
+
+import init, { SMA, RSI } from "../../bindings/wasm/pkg/wickra_wasm.js";
+
+const ready = init();
+
+self.addEventListener("message", async (event) => {
+  await ready;
+  const { panelSlice, indicator } = event.data;
+
+  const results = new Array(panelSlice.length);
+  for (let i = 0; i < panelSlice.length; i++) {
+    const prices = panelSlice[i];
+    const ind = indicator === "sma" ? new SMA(14) : new RSI(14);
+    let last = null;
+    for (let j = 0; j < prices.length; j++) {
+      const v = ind.update(prices[j]);
+      if (v !== null) last = v;
+    }
+    results[i] = last;
+  }
+
+  self.postMessage(results);
+});