test(quality): fix fake tests and add missing coverage

P0 fixes:
- telemetry: rewrite fake tests with real behavior verification (25 tests)
- config: delete copied-source tests, use proper imports (2 deleted)
- persistence: fix try-except pass to verify specific errors

P1 fixes:
- pipeline: add real FixedWindowAlgo tests instead of mocks (12 tests)
- provider: add SessionManager and ToolManager tests (25 tests)
- storage: add S3StorageProvider tests with moto mock (16 tests)
- plugin: add handler action tests for setting inheritance (15 tests)
- rag: add file storage and ZIP processing tests (21 tests)
- vector: add VDB filter conversion tests (30 tests)

P2 fixes:
- pipeline/msgtrun: strengthen assertions for exact message count
- api: add response structure validation in integration tests

New test files:
- provider/test_session_manager.py
- provider/test_tool_manager.py
- storage/test_s3storage.py
- plugin/test_handler_actions.py
- rag/test_file_storage.py
- vector/test_vdb_filter_conversion.py

Source code bugs documented:
- provider: TokenManager.next_token() ZeroDivisionError
- telemetry: send_tasks class variable shared state
- command: empty command IndexError, unused parameters
- utils: funcschema KeyError
- entity: vector.py independent declarative_base

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/unit_tests/pipeline/test_msgtrun.py

@@ -133,7 +133,15 @@ class TestRoundTruncatorProcess:
 
     @pytest.mark.asyncio
     async def test_truncate_exceeds_limit(self):
-        """Messages exceeding max-round should be truncated."""
+        """Messages exceeding max-round should be truncated precisely.
+
+        Algorithm: traverse backwards, collect while current_round < max_round, count user messages as rounds.
+        For max_round=2 with 7 messages (u1, a1, u2, a2, u3, a3, u_current):
+        - Iterate: u_current(r=0<2, collect, r=1), a3(r=1<2, collect), u3(r=1<2, collect, r=2)
+        - a2: r=2 not < 2 → break
+        - Collected reverse: [u_current, a3, u3]
+        - Reversed: [u3, a3, u_current] = 3 messages
+        """
         msgtrun = get_msgtrun_module()
         entities = get_entities_module()
 
@@ -145,6 +153,7 @@ class TestRoundTruncatorProcess:
         await stage.initialize(pipeline_config)
 
         # Create query with many messages exceeding limit
+        # 7 messages = 3 full rounds + 1 current user
         query = text_query("current message")
         query.pipeline_config = pipeline_config
         query.messages = [
@@ -160,9 +169,17 @@ class TestRoundTruncatorProcess:
         result = await stage.process(query, 'ConversationMessageTruncator')
 
         assert result.result_type == entities.ResultType.CONTINUE
-        # Should only keep last 2 rounds (2 user messages)
-        # Each round = user + assistant, so 2 rounds = 4 messages + current = 5
-        assert len(result.new_query.messages) <= 5
+        # Should keep exactly 3 messages: message3, response3, current message
+        messages = result.new_query.messages
+        assert len(messages) == 3
+
+        # Verify exact message content
+        assert messages[0].role == 'user'
+        assert messages[0].content == 'message 3'
+        assert messages[1].role == 'assistant'
+        assert messages[1].content == 'response 3'
+        assert messages[2].role == 'user'
+        assert messages[2].content == 'current message'
 
     @pytest.mark.asyncio
     async def test_truncate_empty_messages(self):