add: comprehensive TDD test infrastructure

- Add Vitest + jsdom testing framework
- Create unit tests for engine.js and generator.js
- Add integration tests for end-to-end workflows
- Include test utilities and setup helpers
- Document testing approach in TESTING.md
- Document all dependencies in DEPENDS.md
- Add Makefile with test targets and dev workflow

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

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

package.json

@@ -0,0 +1,27 @@
+{
+  "name": "timeline-svg-generator",
+  "version": "1.0.0",
+  "description": "Browser-based system for generating multi-lane timelines as SVG graphics",
+  "type": "module",
+  "scripts": {
+    "test": "vitest",
+    "test:watch": "vitest --watch",
+    "test:coverage": "vitest --coverage",
+    "test:ui": "vitest --ui"
+  },
+  "devDependencies": {
+    "@vitest/ui": "^2.1.0",
+    "@vitest/coverage-v8": "^2.1.0",
+    "jsdom": "^25.0.0",
+    "vitest": "^2.1.0"
+  },
+  "keywords": [
+    "timeline",
+    "svg",
+    "visualization",
+    "project-management",
+    "gantt"
+  ],
+  "author": "",
+  "license": "MIT"
+}