fix: create AsyncOpenAI lazily in trajectory_compressor to avoid closed event loop (#4013)

The AsyncOpenAI client was created once at __init__ and stored as an
instance attribute. process_directory() calls asyncio.run() which creates
and closes a fresh event loop. On a second call, the client's httpx
transport is still bound to the closed loop, raising RuntimeError:
"Event loop is closed" — the same pattern fixed by PR #3398 for the
main agent loop.

Create the client lazily in _get_async_client() so each asyncio.run()
gets a client bound to the current loop.

Co-authored-by: binhnt92 <binhnt.ht.92@gmail.com>

trajectory_compressor.py

@@ -375,15 +375,34 @@ class TrajectoryCompressor:
                 raise RuntimeError(
                     f"Missing API key. Set {self.config.api_key_env} "
                     f"environment variable.")
-            from openai import OpenAI, AsyncOpenAI
+            from openai import OpenAI
             self.client = OpenAI(
                 api_key=api_key, base_url=self.config.base_url)
-            self.async_client = AsyncOpenAI(
-                api_key=api_key, base_url=self.config.base_url)
+            # AsyncOpenAI is created lazily in _get_async_client() so it
+            # binds to the current event loop — avoids "Event loop is closed"
+            # when process_directory() is called multiple times (each call
+            # creates a new loop via asyncio.run()).
+            self.async_client = None
+            self._async_client_api_key = api_key
 
         print(f"✅ Initialized summarizer client: {self.config.summarization_model}")
         print(f"   Max concurrent requests: {self.config.max_concurrent_requests}")
 
+    def _get_async_client(self):
+        """Return an AsyncOpenAI client bound to the current event loop.
+
+        Created lazily so that each ``asyncio.run()`` call in
+        ``process_directory()`` gets a client tied to its own loop,
+        avoiding "Event loop is closed" errors on repeated calls.
+        """
+        from openai import AsyncOpenAI
+        # Always create a fresh client so it binds to the running loop.
+        self.async_client = AsyncOpenAI(
+            api_key=self._async_client_api_key,
+            base_url=self.config.base_url,
+        )
+        return self.async_client
+
     def _detect_provider(self) -> str:
         """Detect the provider name from the configured base_url."""
         url = (self.config.base_url or "").lower()
@@ -615,7 +634,7 @@ Write only the summary, starting with "[CONTEXT SUMMARY]:" prefix."""
                         max_tokens=self.config.summary_target_tokens * 2,
                     )
                 else:
-                    response = await self.async_client.chat.completions.create(
+                    response = await self._get_async_client().chat.completions.create(
                         model=self.config.summarization_model,
                         messages=[{"role": "user", "content": prompt}],
                         temperature=self.config.temperature,