feat: improve rate limit error handling with user-friendly messages

- Add rate_limit error type to ErrorInfo classification
- Implement isRateLimitError() and extractRetryAfter() utilities
- Enhance ClaudeProvider error handling with actionable messages
- Add comprehensive test coverage (8 new tests, 162 total passing)

**Problem:**
When hitting API rate limits, users saw cryptic 'exit code 1' errors
with no explanation or guidance on how to resolve the issue.

**Solution:**
- Detect rate limit errors (429) and extract retry-after duration
- Provide clear, user-friendly error messages with:
  * Explanation of what went wrong
  * How long to wait before retrying
  * Actionable tip to reduce concurrency in auto-mode
- Preserve original error details for debugging

**Changes:**
- libs/types: Add 'rate_limit' type and retryAfter field to ErrorInfo
- libs/utils: Add rate limit detection and extraction logic
- apps/server: Enhance ClaudeProvider with better error messages
- tests: Add 8 new test cases covering rate limit scenarios

**Benefits:**
✅ Clear communication - users understand the problem
✅ Actionable guidance - users know how to fix it
✅ Better debugging - original errors preserved
✅ Type safety - proper TypeScript typing
✅ Comprehensive testing - all edge cases covered

See CHANGELOG_RATE_LIMIT_HANDLING.md for detailed documentation.

apps/server/src/providers/claude-provider.ts

@@ -7,6 +7,7 @@
 
 import { query, type Options } from '@anthropic-ai/claude-agent-sdk';
 import { BaseProvider } from './base-provider.js';
+import { classifyError, getUserFriendlyErrorMessage } from '@automaker/utils';
 import type {
   ExecuteOptions,
   ProviderMessage,
@@ -107,9 +108,32 @@ export class ClaudeProvider extends BaseProvider {
         yield msg as ProviderMessage;
       }
     } catch (error) {
-      console.error('[ClaudeProvider] ERROR: executeQuery() error during execution:', error);
-      console.error('[ClaudeProvider] ERROR stack:', (error as Error).stack);
-      throw error;
+      // Enhance error with user-friendly message and classification
+      const errorInfo = classifyError(error);
+      const userMessage = getUserFriendlyErrorMessage(error);
+
+      console.error('[ClaudeProvider] executeQuery() error during execution:', {
+        type: errorInfo.type,
+        message: errorInfo.message,
+        isRateLimit: errorInfo.isRateLimit,
+        retryAfter: errorInfo.retryAfter,
+        stack: (error as Error).stack,
+      });
+
+      // Build enhanced error message with additional guidance for rate limits
+      const message = errorInfo.isRateLimit
+        ? `${userMessage}\n\nTip: If you're running multiple features in auto-mode, consider reducing concurrency (maxConcurrency setting) to avoid hitting rate limits.`
+        : userMessage;
+
+      const enhancedError = new Error(message);
+      (enhancedError as any).originalError = error;
+      (enhancedError as any).type = errorInfo.type;
+
+      if (errorInfo.isRateLimit) {
+        (enhancedError as any).retryAfter = errorInfo.retryAfter;
+      }
+
+      throw enhancedError;
     }
   }