fix: Update test_runner.json to point to build/tests/integration

Integration test modules (.so files) are built in build/tests/integration,
not tests/integration. Updated config to reflect correct path.

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

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

config/test_runner.json

@@ -1,6 +1,6 @@
 {
     "enabled": true,
-    "testDirectory": "tests/integration",
+    "testDirectory": "build/tests/integration",
     "globalTimeoutMs": 300000,
     "stopOnFirstFailure": false,
     "verboseOutput": true,