🧪 Add integration test for /health endpoint

[Trapston3]

🎯 What: The src/server.js missing API integration tests for /health endpoint gap has been addressed. The server instance is conditionally exported from src/server.js allowing it to be effectively closed by test files if needed. Added supertest as a devDependency.

📊 Coverage: A new test block in tests/server.test.js covers making a GET request to /health, checking for a 200 status code, and asserting the expected JSON shape (specifically the existence of uptime, memory, and processID values matching the internal RuntimeSnapshot).

✨ Result: Test coverage improved for the server integration file to include basic sanity checks for the primary health monitoring endpoint.

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PR created automatically by Jules for task 13454337989665841375 started by @Trapston3

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