fix(#151): Fix linting violations in compaction tests

Fixed code review findings:
- Removed unused imports (MagicMock, ContextUsage)
- Fixed import sorting violations

All 41 tests still passing after fixes.

apps/coordinator/tests/test_context_compaction.py

@@ -6,11 +6,11 @@ Context compaction reduces memory usage by:
 3. Measuring context reduction achieved
 """
 
-import pytest
-from unittest.mock import AsyncMock, MagicMock
+from unittest.mock import AsyncMock
 
-from src.context_compaction import ContextCompactor, CompactionResult
-from src.models import ContextUsage
+import pytest
+
+from src.context_compaction import CompactionResult, ContextCompactor
 
 
 class TestContextCompactor:

apps/coordinator/tests/test_context_monitor.py

@@ -325,6 +325,7 @@ class TestContextMonitor:
     ) -> None:
         """Should perform compaction when COMPACT action is triggered."""
         from unittest.mock import patch
+
         from src.context_compaction import CompactionResult
 
         # Mock compaction result
@@ -365,6 +366,7 @@ class TestContextMonitor:
     ) -> None:
         """Should log compaction metrics when compaction is performed."""
         from unittest.mock import patch
+
         from src.context_compaction import CompactionResult
 
         mock_compaction_result = CompactionResult(
@@ -402,6 +404,7 @@ class TestContextMonitor:
     ) -> None:
         """Should handle compaction failure and log error."""
         from unittest.mock import patch
+
         from src.context_compaction import CompactionResult
 
         mock_compaction_result = CompactionResult(