feat: add comprehensive performance benchmark tracking system

- Create benchmark test suites for critical operations:
  - Node loading performance
  - Database query performance
  - Search operations performance
  - Validation performance
  - MCP tool execution performance

- Add GitHub Actions workflow for benchmark tracking:
  - Runs on push to main and PRs
  - Uses github-action-benchmark for historical tracking
  - Comments on PRs with performance results
  - Alerts on >10% performance regressions
  - Stores results in GitHub Pages

- Create benchmark infrastructure:
  - Custom Vitest benchmark configuration
  - JSON reporter for CI results
  - Result formatter for github-action-benchmark
  - Performance threshold documentation

- Add supporting utilities:
  - SQLiteStorageService for benchmark database setup
  - MCPEngine wrapper for testing MCP tools
  - Test factories for generating benchmark data
  - Enhanced NodeRepository with benchmark methods

- Document benchmark system:
  - Comprehensive benchmark guide in docs/BENCHMARKS.md
  - Performance thresholds in .github/BENCHMARK_THRESHOLDS.md
  - README for benchmarks directory
  - Integration with existing test suite

The benchmark system will help monitor performance over time and catch regressions before they reach production.

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

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

vitest.config.benchmark.ts

@@ -0,0 +1,33 @@
+import { defineConfig } from 'vitest/config';
+import path from 'path';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+    include: ['tests/benchmarks/**/*.bench.ts'],
+    benchmark: {
+      // Benchmark specific options
+      include: ['tests/benchmarks/**/*.bench.ts'],
+      reporters: process.env.CI 
+        ? [['./scripts/vitest-benchmark-json-reporter.js', {}]] 
+        : ['default'],
+    },
+    setupFiles: [],
+    pool: 'forks',
+    poolOptions: {
+      forks: {
+        singleFork: true,
+      },
+    },
+    // Increase timeout for benchmarks
+    testTimeout: 120000,
+    hookTimeout: 120000,
+  },
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src'),
+      '@tests': path.resolve(__dirname, './tests'),
+    },
+  },
+});