Hot reload enabled for native servers

Use cases, pain points, and background
It's much easier to develop without having to find terminals and ctrl+c around all the time to adhoc test new code changes.

Description:
We should enable users to test their new code changes without ever spinning up or down their servers.

Design:
There is a way to hot reload fastapi servers. https://fastapi.tiangolo.com/vi/deployment/manually/#run-the-server-program. May be as simple as passing some option to the initial server spinup in nemo_gym/cli.py. We should just be able to watch the entire resources_server/xyz_server folder excluding the .venv.

Out of scope:
Doesn't need to work for all small edge cases. But needs to work for majority of servers.

Acceptance Criteria:

• Implementation of the above. I need to be able to spin up some server, make changes to runtime code, and see it take effect on subsequent queries.
• We need docs on how this is executed so people understand what can be hot reloaded and what cannot be.

Start in nemo_gym/cli.py and trace how resources_server/xyz_server instances are started. Compare that startup path with FastAPI's documented reload approach and determine how the server folder, excluding .venv, is watched. Done means runtime changes affect subsequent queries and the supported hot-reload behavior is documented.