feat(core-shared): add withSpan higher-order helper

packages/core-shared/src/instrumentation/with-span.ts

@@ -0,0 +1,12 @@
+import type { ITracer, SpanOpts } from "./tracer.interface";
+
+export function withSpan<Args extends unknown[], R>(
+  tracer: ITracer,
+  opts: SpanOpts | ((args: Args) => SpanOpts),
+  fn: (...args: Args) => Promise<R>,
+): (...args: Args) => Promise<R> {
+  return (...args) => {
+    const resolved = typeof opts === "function" ? opts(args) : opts;
+    return tracer.startSpan(resolved, () => fn(...args));
+  };
+}