feat: add WebGPU DAS backend

packages/webgpu-kernels/compute.js

@@ -0,0 +1,58 @@
+import { computeDasMap } from "../acoustics-core/das.js";
+import { computeDasWebGpu } from "./das.js";
+import { isRecoverableWebGpuError } from "./device.js";
+
+function createAbortError(signal) {
+  if (signal?.reason instanceof Error && signal.reason.name === "AbortError") return signal.reason;
+  const error = new Error("DAS 계산이 취소되었습니다.");
+  error.name = "AbortError";
+  return error;
+}
+
+function throwIfAborted(signal) {
+  if (signal?.aborted) throw createAbortError(signal);
+}
+
+/**
+ * Execute the requested DAS backend. `auto` falls back only for typed WebGPU
+ * operational errors; invalid inputs and AbortError remain visible to callers.
+ */
+export async function computeDasWithBackend(options, dependencies = {}) {
+  const computeGpu = dependencies.computeGpu ?? computeDasWebGpu;
+  const computeCpu = dependencies.computeCpu ?? computeDasMap;
+  const requestedBackend = options?.experiment?.beamforming?.backend ?? "auto";
+
+  if (requestedBackend === "cpu") return computeCpu(options);
+  if (requestedBackend === "webgpu") return computeGpu(options);
+  if (requestedBackend !== "auto") {
+    throw new TypeError(`지원하지 않는 DAS backend입니다: ${requestedBackend}`);
+  }
+
+  try {
+    return await computeGpu(options);
+  } catch (gpuError) {
+    if (!isRecoverableWebGpuError(gpuError)) throw gpuError;
+    throwIfAborted(options.signal);
+    options.onFallback?.({ from: "webgpu", to: "cpu", error: gpuError });
+    throwIfAborted(options.signal);
+    try {
+      const cpuResult = await computeCpu(options);
+      return {
+        ...cpuResult,
+        requestedBackend: "auto",
+        fallback: {
+          from: "webgpu",
+          code: gpuError.code,
+          message: gpuError.message,
+        },
+      };
+    } catch (cpuError) {
+      if (cpuError?.name === "AbortError") throw cpuError;
+      throwIfAborted(options.signal);
+      throw new AggregateError(
+        [gpuError, cpuError],
+        `WebGPU 실행 실패 후 CPU fallback도 실패했습니다: ${cpuError.message}`,
+      );
+    }
+  }
+}