terminus2 agent (#343)

* [Feature] Support terminus2 adapter

* [Refactor] Wrap harbor.Terminus2 in Terminus2Adapter

- Replace terminal-bench-based wrapping with a thin adapter over
  harbor.agents.terminus_2.Terminus2; harbor's LiteLLM layer sets
  reraise=True, so auth/rate-limit errors surface instead of being
  swallowed by nested RetryError.
- Bundle a lazy LocalSandboxEnvironment factory exposing harbor's
  BaseEnvironment via local subprocess/shutil — the adapter runs inside
  the lagent sandbox daemon, and lazy build keeps `import lagent.adapters`
  working without harbor on PYTHONPATH.

* [Feature] Support get_messages in Terminus2Adapter

* [Fix] Capture terminus2 trajectory on timeout and support whitebox get_messages

* [Refactor] Route Terminus2Adapter LLM calls solely through the proxy

- Drop base_url/api_key from Terminus2Adapter.__init__; always use
  self.proxy.url and sk-proxy-{session_id}.  As a black-box adapter, an
  explicit base_url/api_key alongside the proxy only muddies which endpoint
  is actually used.
- Require the SessionClient proxy: setup() raises if it is missing, and the
  whitebox (proxy is None) fallbacks in run_external_async / get_messages are
  removed.
- Remove SessionClient.get_records; get_messages reads self.proxy._records
  directly so the per-turn dedup logic stays in the adapter, not the proxy.

Author: liujiangning30

lagent/adapters/__init__.py

@@ -7,6 +7,7 @@
 from .openhands import OpenHandsAdapter
 from .proxy import SessionClient
 from .sdk_adapter import SDKAgentAdapter
+from .terminus2 import Terminus2Adapter
 
 __all__ = [
     'BaseExternalAgent',
@@ -19,4 +20,5 @@
     'SDKAgentAdapter',
     'MiniSWEAgentAdapter',
     'SessionClient',
+    'Terminus2Adapter',
 ]