fix: Rename SlidingWindowCompactor to LlmEventSummarizer and refine its docstring

The class is now named `LlmEventSummarizer` to better reflect that its primary function is to use an LLM to summarize events. The docstring has been updated to clarify that this class is responsible *only* for the LLM-based summarization of a given set of events, while the logic for determining *when* and *which* events form the sliding window is handled by an external component, such as an ADK Runner.

PiperOrigin-RevId: 815976264

tests/unittests/apps/test_compaction.py

@@ -20,7 +20,7 @@ from google.adk.agents.base_agent import BaseAgent
 from google.adk.apps.app import App
 from google.adk.apps.app import EventsCompactionConfig
 from google.adk.apps.compaction import _run_compaction_for_sliding_window
-from google.adk.apps.sliding_window_compactor import SlidingWindowCompactor
+from google.adk.apps.llm_event_summarizer import LlmEventSummarizer
 from google.adk.events.event import Event
 from google.adk.events.event_actions import EventActions
 from google.adk.events.event_actions import EventCompaction
@@ -38,7 +38,7 @@ class TestCompaction(unittest.IsolatedAsyncioTestCase):
 
   def setUp(self):
     self.mock_session_service = AsyncMock(spec=BaseSessionService)
-    self.mock_compactor = AsyncMock(spec=SlidingWindowCompactor)
+    self.mock_compactor = AsyncMock(spec=LlmEventSummarizer)
 
   def _create_event(
       self, timestamp: float, invocation_id: str, text: str

tests/unittests/apps/test_llm_event_summarizer.py

@@ -16,7 +16,7 @@ import unittest
 from unittest.mock import AsyncMock
 from unittest.mock import Mock
 
-from google.adk.apps.sliding_window_compactor import SlidingWindowCompactor
+from google.adk.apps.llm_event_summarizer import LlmEventSummarizer
 from google.adk.events.event import Event
 from google.adk.events.event_actions import EventActions
 from google.adk.events.event_actions import EventCompaction
@@ -32,12 +32,12 @@ import pytest
 @pytest.mark.parametrize(
     'env_variables', ['GOOGLE_AI', 'VERTEX'], indirect=True
 )
-class TestSlidingWindowCompactor(unittest.IsolatedAsyncioTestCase):
+class TestLlmEventSummarizer(unittest.IsolatedAsyncioTestCase):
 
   def setUp(self):
     self.mock_llm = AsyncMock(spec=BaseLlm)
     self.mock_llm.model = 'test-model'
-    self.compactor = SlidingWindowCompactor(llm=self.mock_llm)
+    self.compactor = LlmEventSummarizer(llm=self.mock_llm)
 
   def _create_event(
       self, timestamp: float, text: str, author: str = 'user'