Improve error formatting in tests

- Replace [object Object] errors with readable messages by using robust error formatting across test suites
- Introduce formatTestError helper and apply it in all catch blocks and error throws
- Update approvalPipelineTests and related suites to utilize improved error extraction for better debugging

src/lib/integrationTests/formatTestError.ts

@@ -0,0 +1,59 @@
+/**
+ * Test Error Formatting Utility
+ * 
+ * Provides robust error formatting for test results to avoid "[object Object]" messages
+ */
+
+/**
+ * Format error for test result display
+ * Handles Error objects, PostgresError objects, and plain objects
+ * 
+ * @param error - Any error value thrown in a test
+ * @returns Formatted, human-readable error string
+ */
+export function formatTestError(error: unknown): string {
+  // Standard Error objects
+  if (error instanceof Error) {
+    return error.message;
+  }
+  
+  // Object-like errors (PostgresError, custom error objects, etc.)
+  if (typeof error === 'object' && error !== null) {
+    const err = error as any;
+    
+    // Try common error message properties
+    if (err.message && typeof err.message === 'string') {
+      return err.message;
+    }
+    
+    // Some errors nest the actual error in an 'error' property
+    if (err.error) {
+      return formatTestError(err.error);
+    }
+    
+    // Some APIs use 'msg' instead of 'message'
+    if (err.msg && typeof err.msg === 'string') {
+      return err.msg;
+    }
+    
+    // Supabase errors might have details
+    if (err.details && typeof err.details === 'string') {
+      return `${err.message || 'Error'}: ${err.details}`;
+    }
+    
+    // Last resort: stringify the entire object
+    try {
+      const stringified = JSON.stringify(error, null, 2);
+      // If it's too long, truncate it
+      return stringified.length > 500 
+        ? stringified.substring(0, 500) + '... (truncated)'
+        : stringified;
+    } catch {
+      // JSON.stringify can fail on circular references
+      return String(error);
+    }
+  }
+  
+  // Primitive values (strings, numbers, etc.)
+  return String(error);
+}