Offline Init Part 4 of 4: Add shared test data round-trip tests for offline initialization (#119)

* Add shared test data round-trip tests for offline initialization

Validates offline initialization using the shared UFC and bandit test data:
- Initializes SDK via API, exports configuration
- Resets module state and re-initializes using offlineInit
- Runs all shared test cases against offline-initialized client

This ensures exported configurations can be successfully used to bootstrap
new SDK instances with identical behavior.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Fix offlineInit test structure to share mock server with round-trip tests

Move offlineInit describe block inside the main 'EppoClient E2E test' block
so that round-trip tests have access to the mock API server started in
beforeAll.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Bump version to 3.13.0

Non-breaking change adding new offline initialization functionality.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: aarsilv

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@eppo/node-server-sdk",
-  "version": "3.12.2",
+  "version": "3.13.0",
   "description": "Eppo node server SDK",
   "main": "dist/index.js",
   "files": [