feat: add @automaker/utils package

- Extract error handling utilities (isAbortError, classifyError, etc.)
- Extract conversation utilities (formatHistoryAsText, etc.)
- Extract image handling utilities (readImageAsBase64, etc.)
- Extract prompt building utilities (buildPromptWithImages)
- Extract logger utilities (createLogger, setLogLevel)
- Extract file system utilities (mkdirSafe, existsSafe)

All utilities now use @automaker/types for type imports.
Provides shared utility functions for both server and UI.

Dependencies: @automaker/types

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

libs/utils/src/error-handler.ts

@@ -0,0 +1,110 @@
+/**
+ * Error handling utilities for standardized error classification
+ *
+ * Provides utilities for:
+ * - Detecting abort/cancellation errors
+ * - Detecting authentication errors
+ * - Classifying errors by type
+ * - Generating user-friendly error messages
+ */
+
+import type { ErrorType, ErrorInfo } from '@automaker/types';
+
+/**
+ * Check if an error is an abort/cancellation error
+ *
+ * @param error - The error to check
+ * @returns True if the error is an abort error
+ */
+export function isAbortError(error: unknown): boolean {
+  return (
+    error instanceof Error &&
+    (error.name === "AbortError" || error.message.includes("abort"))
+  );
+}
+
+/**
+ * Check if an error is a user-initiated cancellation
+ *
+ * @param errorMessage - The error message to check
+ * @returns True if the error is a user-initiated cancellation
+ */
+export function isCancellationError(errorMessage: string): boolean {
+  const lowerMessage = errorMessage.toLowerCase();
+  return (
+    lowerMessage.includes("cancelled") ||
+    lowerMessage.includes("canceled") ||
+    lowerMessage.includes("stopped") ||
+    lowerMessage.includes("aborted")
+  );
+}
+
+/**
+ * Check if an error is an authentication/API key error
+ *
+ * @param errorMessage - The error message to check
+ * @returns True if the error is authentication-related
+ */
+export function isAuthenticationError(errorMessage: string): boolean {
+  return (
+    errorMessage.includes("Authentication failed") ||
+    errorMessage.includes("Invalid API key") ||
+    errorMessage.includes("authentication_failed") ||
+    errorMessage.includes("Fix external API key")
+  );
+}
+
+/**
+ * Classify an error into a specific type
+ *
+ * @param error - The error to classify
+ * @returns Classified error information
+ */
+export function classifyError(error: unknown): ErrorInfo {
+  const message = error instanceof Error ? error.message : String(error || "Unknown error");
+  const isAbort = isAbortError(error);
+  const isAuth = isAuthenticationError(message);
+  const isCancellation = isCancellationError(message);
+
+  let type: ErrorType;
+  if (isAuth) {
+    type = "authentication";
+  } else if (isAbort) {
+    type = "abort";
+  } else if (isCancellation) {
+    type = "cancellation";
+  } else if (error instanceof Error) {
+    type = "execution";
+  } else {
+    type = "unknown";
+  }
+
+  return {
+    type,
+    message,
+    isAbort,
+    isAuth,
+    isCancellation,
+    originalError: error,
+  };
+}
+
+/**
+ * Get a user-friendly error message
+ *
+ * @param error - The error to convert
+ * @returns User-friendly error message
+ */
+export function getUserFriendlyErrorMessage(error: unknown): string {
+  const info = classifyError(error);
+
+  if (info.isAbort) {
+    return "Operation was cancelled";
+  }
+
+  if (info.isAuth) {
+    return "Authentication failed. Please check your API key.";
+  }
+
+  return info.message;
+}