docs: add MongoDB pool settings and advanced test scripts

README.md:
- Add MONGO_POOL_SIZE, MONGO_MIN_POOL_SIZE, MONGO_MAX_IDLE_TIME_MS
  to Core section for production tuning

CONTRIBUTING.md:
- Add 'Advanced Test Scripts' section documenting:
  - test:stress for concurrent write testing
  - test:flaky variants for detecting flaky tests
  - test:timing for finding slow tests

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

CONTRIBUTING.md

@@ -160,6 +160,27 @@ NODE_ENV=test npm run test:integration
 NODE_ENV=test npm test -- --grep "treatments"
 ```
 
+### Advanced Test Scripts
+
+For diagnosing test issues and ensuring reliability:
+
+```bash
+# Run stress tests for concurrent write operations
+NODE_ENV=test npm run test:stress
+
+# Detect flaky tests by running multiple iterations
+NODE_ENV=test npm run test:flaky           # Default iterations
+NODE_ENV=test npm run test:flaky:quick     # 3 iterations
+NODE_ENV=test npm run test:flaky:thorough  # 20 iterations
+
+# Run specific flaky test harnesses
+NODE_ENV=test npm run test:flaky:entries   # Entries isolation tests
+NODE_ENV=test npm run test:flaky:socket    # Socket isolation tests
+
+# Enable timing warnings to find slow tests
+NODE_ENV=test npm run test:timing
+```
+
 You can create a `my.test.env` file based on `ci.test.env` for local testing:
 
 ```bash

README.md

@@ -289,6 +289,9 @@ autonomy for your data:
   * `MONGO_PROFILE_COLLECTION`(`profile`) - The collection used to store your profiles
   * `MONGO_FOOD_COLLECTION`(`food`) - The collection used to store your food database
   * `MONGO_ACTIVITY_COLLECTION`(`activity`) - The collection used to store activity data
+  * `MONGO_POOL_SIZE` (`10`) - MongoDB connection pool size. Reduce for resource-constrained environments.
+  * `MONGO_MIN_POOL_SIZE` (`1`) - Minimum pool connections to keep open.
+  * `MONGO_MAX_IDLE_TIME_MS` (`10000`) - Max idle time (ms) before closing a connection.
   * `PORT` (`1337`) - The port that the node.js application will listen on.
   * `HOSTNAME` - The hostname that the node.js application will listen on, null by default for any hostname for IPv6 you may need to use `::`.
   * `SSL_KEY` - Path to your ssl key file, so that ssl(https) can be enabled directly in node.js. If using Let's Encrypt, make this variable the path to your privkey.pem file (private key).