chore(context): refactor for consistency, optimize formatting, and simplify logic

- Cleaned up unnecessary comments in `__all__` definitions for better readability.
- Adjusted indentation and formatting across modules for improved clarity (e.g., long lines, logical grouping).
- Simplified conditional expressions and inline comments for context scoring and ranking.
- Replaced some hard-coded values with type-safe annotations (e.g., `ClassVar`).
- Removed unused imports and ensured consistent usage across test files.
- Updated `test_score_not_cached_on_context` to clarify caching behavior.
- Improved truncation strategy logic and marker handling.

backend/tests/services/context/test_compression.py

@@ -2,16 +2,15 @@
 
 import pytest
 
+from app.services.context.budget import BudgetAllocator
 from app.services.context.compression import (
     ContextCompressor,
     TruncationResult,
     TruncationStrategy,
 )
-from app.services.context.budget import BudgetAllocator, TokenBudget
 from app.services.context.types import (
     ContextType,
     KnowledgeContext,
-    SystemContext,
     TaskContext,
 )
 
@@ -113,7 +112,7 @@ class TestTruncationStrategy:
 
         assert result.truncated is True
         assert len(result.content) < len(content)
-        assert strategy.TRUNCATION_MARKER in result.content
+        assert strategy.truncation_marker in result.content
 
     @pytest.mark.asyncio
     async def test_truncate_middle_strategy(self) -> None:
@@ -126,7 +125,7 @@ class TestTruncationStrategy:
         )
 
         assert result.truncated is True
-        assert strategy.TRUNCATION_MARKER in result.content
+        assert strategy.truncation_marker in result.content
 
     @pytest.mark.asyncio
     async def test_truncate_sentence_strategy(self) -> None:
@@ -140,7 +139,9 @@ class TestTruncationStrategy:
 
         assert result.truncated is True
         # Should cut at sentence boundary
-        assert result.content.endswith(".") or strategy.TRUNCATION_MARKER in result.content
+        assert (
+            result.content.endswith(".") or strategy.truncation_marker in result.content
+        )
 
 
 class TestContextCompressor:
@@ -235,10 +236,12 @@ class TestTruncationEdgeCases:
         content = "Some content to truncate"
 
         # max_tokens less than marker tokens should return just marker
-        result = await strategy.truncate_to_tokens(content, max_tokens=1, strategy="end")
+        result = await strategy.truncate_to_tokens(
+            content, max_tokens=1, strategy="end"
+        )
 
         # Should handle gracefully without crashing
-        assert strategy.TRUNCATION_MARKER in result.content or result.content == content
+        assert strategy.truncation_marker in result.content or result.content == content
 
     @pytest.mark.asyncio
     async def test_truncate_with_content_that_has_zero_tokens(self) -> None:
@@ -249,7 +252,7 @@ class TestTruncationEdgeCases:
         result = await strategy.truncate_to_tokens("a", max_tokens=100)
 
         # Should not raise ZeroDivisionError
-        assert result.content in ("a", "a" + strategy.TRUNCATION_MARKER)
+        assert result.content in ("a", "a" + strategy.truncation_marker)
 
     @pytest.mark.asyncio
     async def test_get_content_for_tokens_zero_target(self) -> None: