CLI: add nodes canvas snapshot + duration parsing

src/cli/nodes-canvas.ts

@@ -0,0 +1,41 @@
+import { randomUUID } from "node:crypto";
+import * as os from "node:os";
+import * as path from "node:path";
+
+export type CanvasSnapshotPayload = {
+  format: string;
+  base64: string;
+};
+
+function asRecord(value: unknown): Record<string, unknown> {
+  return typeof value === "object" && value !== null
+    ? (value as Record<string, unknown>)
+    : {};
+}
+
+function asString(value: unknown): string | undefined {
+  return typeof value === "string" ? value : undefined;
+}
+
+export function parseCanvasSnapshotPayload(
+  value: unknown,
+): CanvasSnapshotPayload {
+  const obj = asRecord(value);
+  const format = asString(obj.format);
+  const base64 = asString(obj.base64);
+  if (!format || !base64) {
+    throw new Error("invalid canvas.snapshot payload");
+  }
+  return { format, base64 };
+}
+
+export function canvasSnapshotTempPath(opts: {
+  ext: string;
+  tmpDir?: string;
+  id?: string;
+}) {
+  const tmpDir = opts.tmpDir ?? os.tmpdir();
+  const id = opts.id ?? randomUUID();
+  const ext = opts.ext.startsWith(".") ? opts.ext : `.${opts.ext}`;
+  return path.join(tmpDir, `clawdis-canvas-snapshot-${id}${ext}`);
+}