Refresh TEE configs periodically

[adambalogh]

• create TEEConnection class to encapsulate connection refresh
• refresh TEE configs in background and switch to new one in case current one has been disabled

[Copilot]

Pull request overview

This PR introduces a dedicated TEE connection abstraction that can periodically re-resolve TEE configuration from the on-chain registry, and updates the LLM client and tests to use that abstraction.

Changes:

• Added tee_connection.py with RegistryTEEConnection (background refresh + reconnect) and StaticTEEConnection (fixed URL).
• Refactored LLM to use the new connection layer (including a new LLM.from_url(...) constructor).
• Added/updated tests to cover connection lifecycle, refresh behavior, and updated LLM internals.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/opengradient/client/tee_connection.py	New connection abstraction with reconnect + background refresh loop.
src/opengradient/client/llm.py	Refactor to delegate TEE endpoint + client lifecycle to TEEConnectionInterface; adds from_url.
src/opengradient/client/tee_registry.py	Makes TEEEndpoint frozen/immutable.
tests/tee_connection_test.py	New test suite for connection lifecycle, reconnect, refresh loop, and close semantics.
tests/llm_test.py	Updates patching and expectations to align with the new connection layer.
tests/client_test.py	Updates initialization assertions to reference the new connection state.

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