fix: downgrade chai to v4 for CommonJS compatibility

Author: jsonify

AUTOMATED_TESTING.md

@@ -211,3 +211,29 @@ git push
 - Standard practice for all package managers (npm, yarn, pnpm)
 
 **Note**: The `pnpm-lock.yaml` file should **always** be committed to version control, never ignored.
+
+### "require() of ES Module ... chai/index.js ... not supported"
+
+**Cause**: Chai v6+ is an ES Module, but the tests are compiled to CommonJS
+
+**Solution**: Use Chai v4 (the last CommonJS-compatible version)
+
+```bash
+# Downgrade chai to v4
+pnpm remove chai @types/chai
+pnpm add -D chai@4 @types/chai@4
+
+# Regenerate lockfile
+pnpm install
+```
+
+**Why Chai 4?**
+- ✅ CommonJS compatible (works with TypeScript CommonJS output)
+- ✅ Stable and mature (used by millions of projects)
+- ✅ Same API as Chai 6 for our use cases
+- ✅ No breaking changes needed in tests
+
+**Note**: The project uses TypeScript with CommonJS modules. To use Chai 6+, you would need to:
+- Switch to ES Modules in tsconfig.json (set `"module": "ES2020"`)
+- Update all imports to use `import` syntax
+- Configure Mocha for ESM

package.json

@@ -303,12 +303,12 @@
   },
   "packageManager": "pnpm@8.15.9",
   "devDependencies": {
-    "@types/chai": "^5.2.2",
+    "@types/chai": "4",
     "@types/mocha": "^10.0.10",
     "@types/node": "^18.0.0",
     "@types/vscode": "^1.80.0",
     "@vscode/test-electron": "^2.5.2",
-    "chai": "^6.2.0",
+    "chai": "4",
     "conventional-changelog-cli": "^5.0.0",
     "glob": "^11.0.3",
     "mocha": "^11.7.4",