Feature Request: Make PocketIC Server TTL configurable to support watch mode

[jneums]

Problem:
The PocketIC server currently has a hardcoded idle timeout. While this is great for preventing orphaned processes in single-run CI environments, it makes the library difficult to use in a standard local development workflow with --watch mode (e.g., vitest --watch)

If a developer is using a globalSetup file to start a single server instance for the test run, the server will shut down after a minute of inactivity. When the developer saves a file to trigger a re-run, the tests fail with an ECONNREFUSED error because the server is no longer running.

Steps to Reproduce:

1. Configure Vitest to use a globalSetup file that calls PocketIcServer.start().
2. Run vitest --watch. The first run succeeds.
3. Wait for ~90 seconds without saving any files.
4. Save a test file to trigger a re-run.
5. The test run fails because it cannot connect to the server.

Proposed Solution:
Expose a configuration option in the PocketIcServer.start() method to control the idle timeout. For example:

await PocketIcServer.start({
  // Allow setting the TTL in milliseconds.
  // A value of 0 or null could disable the timeout entirely.
  ttl: 3_600_000, // 1 hour
});

This would be a non-breaking change that would significantly improve the developer experience for local testing.

Current Workaround:
Not using watch mode and just triggering test manually.