merge: wave 2 executor (01-02) into main

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

paperclip-reference/server/src/errors.ts

@@ -0,0 +1,34 @@
+export class HttpError extends Error {
+  status: number;
+  details?: unknown;
+
+  constructor(status: number, message: string, details?: unknown) {
+    super(message);
+    this.status = status;
+    this.details = details;
+  }
+}
+
+export function badRequest(message: string, details?: unknown) {
+  return new HttpError(400, message, details);
+}
+
+export function unauthorized(message = "Unauthorized") {
+  return new HttpError(401, message);
+}
+
+export function forbidden(message = "Forbidden") {
+  return new HttpError(403, message);
+}
+
+export function notFound(message = "Not found") {
+  return new HttpError(404, message);
+}
+
+export function conflict(message: string, details?: unknown) {
+  return new HttpError(409, message, details);
+}
+
+export function unprocessable(message: string, details?: unknown) {
+  return new HttpError(422, message, details);
+}