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>

codecov.yml

@@ -0,0 +1,53 @@
+codecov:
+  require_ci_to_pass: yes
+
+coverage:
+  precision: 2
+  round: down
+  range: "70...100"
+
+  status:
+    project:
+      default:
+        target: 80%
+        threshold: 1%
+        base: auto
+        if_not_found: success
+        if_ci_failed: error
+        informational: false
+        only_pulls: false
+    patch:
+      default:
+        target: 80%
+        threshold: 1%
+        base: auto
+        if_not_found: success
+        if_ci_failed: error
+        informational: false
+        only_pulls: false
+
+parsers:
+  gcov:
+    branch_detection:
+      conditional: yes
+      loop: yes
+      method: no
+      macro: no
+
+comment:
+  layout: "reach,diff,flags,files,footer"
+  behavior: default
+  require_changes: false
+  require_base: false
+  require_head: true
+
+ignore:
+  - "node_modules/**/*"
+  - "dist/**/*"
+  - "tests/**/*"
+  - "scripts/**/*"
+  - "**/*.test.ts"
+  - "**/*.spec.ts"
+  - "src/mcp/index.ts"
+  - "src/http-server.ts"
+  - "src/http-server-single-session.ts"