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_assembly.py

@@ -5,10 +5,9 @@ from datetime import UTC, datetime
 import pytest
 
 from app.services.context.assembly import ContextPipeline, PipelineMetrics
-from app.services.context.budget import BudgetAllocator, TokenBudget
+from app.services.context.budget import TokenBudget
 from app.services.context.types import (
     AssembledContext,
-    ContextType,
     ConversationContext,
     KnowledgeContext,
     MessageRole,
@@ -354,7 +353,10 @@ class TestContextPipelineFormatting:
 
         if result.context_count > 0:
             assert "<conversation_history>" in result.content
-            assert '<message role="user">' in result.content or 'role="user"' in result.content
+            assert (
+                '<message role="user">' in result.content
+                or 'role="user"' in result.content
+            )
 
     @pytest.mark.asyncio
     async def test_format_tool_results(self) -> None:
@@ -474,6 +476,10 @@ class TestContextPipelineIntegration:
                 assert system_pos < task_pos
             if task_pos >= 0 and knowledge_pos >= 0:
                 assert task_pos < knowledge_pos
+            if knowledge_pos >= 0 and conversation_pos >= 0:
+                assert knowledge_pos < conversation_pos
+            if conversation_pos >= 0 and tool_pos >= 0:
+                assert conversation_pos < tool_pos
 
     @pytest.mark.asyncio
     async def test_excluded_contexts_tracked(self) -> None: