refactor: add TypeScript interfaces for test response types

Replace 'as any' type assertions with proper TypeScript interfaces for improved type safety in Phase 8 integration tests.

Changes:
- Created response-types.ts with comprehensive interfaces for all response types
- Updated health-check.test.ts to use HealthCheckResponse interface
- Updated list-tools.test.ts to use ListToolsResponse interface
- Updated diagnostic.test.ts to use DiagnosticResponse interface
- Added null-safety checks for optional fields (data.debug)
- Used non-null assertions (!) for values verified with expect().toBeDefined()
- Removed unnecessary 'as any' casts throughout test files

Benefits:
- Better type safety and IDE autocomplete
- Catches potential type mismatches at compile time
- More maintainable and self-documenting code
- Consistent with code review recommendation

All 19 tests still passing with full type safety.

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

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

tests/integration/n8n-api/utils/response-types.ts

@@ -0,0 +1,202 @@
+/**
+ * TypeScript interfaces for n8n API and MCP handler responses
+ * Used in integration tests to provide type safety
+ */
+
+// ======================================================================
+// System Tool Response Types
+// ======================================================================
+
+export interface HealthCheckResponse {
+  status: string;
+  instanceId?: string;
+  n8nVersion?: string;
+  features?: Record<string, any>;
+  apiUrl: string;
+  mcpVersion: string;
+  supportedN8nVersion?: string;
+  versionNote?: string;
+  [key: string]: any; // Allow dynamic property access for optional field checks
+}
+
+export interface ToolDefinition {
+  name: string;
+  description: string;
+}
+
+export interface ToolCategory {
+  category: string;
+  tools: ToolDefinition[];
+}
+
+export interface ApiConfiguration {
+  apiUrl: string;
+  timeout: number;
+  maxRetries: number;
+}
+
+export interface ListToolsResponse {
+  tools: ToolCategory[];
+  apiConfigured: boolean;
+  configuration?: ApiConfiguration | null;
+  limitations: string[];
+}
+
+export interface ApiStatus {
+  configured: boolean;
+  connected: boolean;
+  error?: string | null;
+  version?: string | null;
+}
+
+export interface ToolsAvailability {
+  documentationTools: {
+    count: number;
+    enabled: boolean;
+    description: string;
+  };
+  managementTools: {
+    count: number;
+    enabled: boolean;
+    description: string;
+  };
+  totalAvailable: number;
+}
+
+export interface DebugInfo {
+  processEnv: string[];
+  nodeVersion: string;
+  platform: string;
+  workingDirectory: string;
+}
+
+export interface DiagnosticResponse {
+  timestamp: string;
+  environment: {
+    N8N_API_URL: string | null;
+    N8N_API_KEY: string | null;
+    NODE_ENV: string;
+    MCP_MODE: string;
+  };
+  apiConfiguration: {
+    configured: boolean;
+    status: ApiStatus;
+    config?: {
+      baseUrl: string;
+      timeout: number;
+      maxRetries: number;
+    } | null;
+  };
+  toolsAvailability: ToolsAvailability;
+  troubleshooting: {
+    steps: string[];
+    documentation: string;
+  };
+  debug?: DebugInfo;
+  [key: string]: any; // Allow dynamic property access for optional field checks
+}
+
+// ======================================================================
+// Execution Response Types
+// ======================================================================
+
+export interface ExecutionData {
+  id: string;
+  status?: 'success' | 'error' | 'running' | 'waiting';
+  mode?: string;
+  startedAt?: string;
+  stoppedAt?: string;
+  workflowId?: string;
+  data?: any;
+}
+
+export interface ListExecutionsResponse {
+  executions: ExecutionData[];
+  returned: number;
+  nextCursor?: string;
+  hasMore: boolean;
+  _note?: string;
+}
+
+// ======================================================================
+// Workflow Response Types
+// ======================================================================
+
+export interface WorkflowNode {
+  id: string;
+  name: string;
+  type: string;
+  typeVersion: number;
+  position: [number, number];
+  parameters: Record<string, any>;
+  credentials?: Record<string, any>;
+  disabled?: boolean;
+}
+
+export interface WorkflowConnections {
+  [key: string]: any;
+}
+
+export interface WorkflowData {
+  id: string;
+  name: string;
+  active: boolean;
+  nodes: WorkflowNode[];
+  connections: WorkflowConnections;
+  settings?: Record<string, any>;
+  staticData?: Record<string, any>;
+  tags?: string[];
+  versionId?: string;
+  createdAt?: string;
+  updatedAt?: string;
+}
+
+export interface ValidationError {
+  nodeId?: string;
+  nodeName?: string;
+  field?: string;
+  message: string;
+  type?: string;
+}
+
+export interface ValidationWarning {
+  nodeId?: string;
+  nodeName?: string;
+  message: string;
+  type?: string;
+}
+
+export interface ValidateWorkflowResponse {
+  valid: boolean;
+  errors?: ValidationError[];
+  warnings?: ValidationWarning[];
+  errorCount?: number;
+  warningCount?: number;
+  summary?: string;
+}
+
+export interface AutofixChange {
+  nodeId: string;
+  nodeName: string;
+  field: string;
+  oldValue: any;
+  newValue: any;
+  reason: string;
+}
+
+export interface AutofixSuggestion {
+  fixType: string;
+  nodeId: string;
+  nodeName: string;
+  description: string;
+  confidence: 'high' | 'medium' | 'low';
+  changes: AutofixChange[];
+}
+
+export interface AutofixResponse {
+  appliedFixes?: number;
+  suggestions?: AutofixSuggestion[];
+  workflow?: WorkflowData;
+  summary?: string;
+  preview?: boolean;
+}