test: implement comprehensive testing improvements from PR #104 review

Major improvements based on comprehensive test suite review:

Test Fixes:
- Fix all 78 failing tests across logger, MSW, and validator tests
- Fix console spy management in logger tests with proper DEBUG env handling
- Fix MSW test environment restoration in session-management.test.ts
- Fix workflow validator tests by adding proper node connections
- Fix mock setup issues in edge case tests

Test Organization:
- Split large config-validator.test.ts (1,075 lines) into 4 focused files
- Rename 63+ tests to follow "should X when Y" naming convention
- Add comprehensive edge case test files for all major validators
- Create tests/README.md with testing guidelines and best practices

New Features:
- Add ConfigValidator.validateBatch() method for bulk validation
- Add edge case coverage for null/undefined, boundaries, invalid data
- Add CI-aware performance test timeouts
- Add JSDoc comments to test utilities and factories
- Add workflow duplicate node name validation tests

Results:
- All tests passing: 1,356 passed, 19 skipped
- Test coverage: 85.34% statements, 85.3% branches
- From 78 failures to 0 failures

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

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

tests/integration/mcp-protocol/session-management.test.ts

@@ -4,12 +4,22 @@ import { Client } from '@modelcontextprotocol/sdk/client/index.js';
 import { TestableN8NMCPServer } from './test-helpers';
 
 describe('MCP Session Management', { timeout: 15000 }, () => {
+  let originalMswEnabled: string | undefined;
+  
   beforeAll(() => {
+    // Save original value
+    originalMswEnabled = process.env.MSW_ENABLED;
     // Disable MSW for these integration tests
     process.env.MSW_ENABLED = 'false';
   });
 
   afterAll(async () => {
+    // Restore original value
+    if (originalMswEnabled !== undefined) {
+      process.env.MSW_ENABLED = originalMswEnabled;
+    } else {
+      delete process.env.MSW_ENABLED;
+    }
     // Clean up any shared resources
     await TestableN8NMCPServer.shutdownShared();
   });