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/app/services/context/prioritization/ranker.py

@@ -11,7 +11,7 @@ from typing import TYPE_CHECKING, Any
 from ..budget import TokenBudget, TokenCalculator
 from ..config import ContextSettings, get_context_settings
 from ..scoring.composite import CompositeScorer, ScoredContext
-from ..types import BaseContext
+from ..types import BaseContext, ContextPriority
 
 if TYPE_CHECKING:
     pass
@@ -111,8 +111,8 @@ class ContextRanker:
 
         if ensure_required:
             for sc in scored_contexts:
-                # CRITICAL priority (100) contexts are always included
-                if sc.context.priority >= 100:
+                # CRITICAL priority (150) contexts are always included
+                if sc.context.priority >= ContextPriority.CRITICAL.value:
                     required.append(sc)
                 else:
                     optional.append(sc)
@@ -239,9 +239,7 @@ class ContextRanker:
         import asyncio
 
         # Find contexts needing counts
-        contexts_needing_counts = [
-            ctx for ctx in contexts if ctx.token_count is None
-        ]
+        contexts_needing_counts = [ctx for ctx in contexts if ctx.token_count is None]
 
         if not contexts_needing_counts:
             return
@@ -254,7 +252,7 @@ class ContextRanker:
         counts = await asyncio.gather(*tasks)
 
         # Assign counts back
-        for ctx, count in zip(contexts_needing_counts, counts):
+        for ctx, count in zip(contexts_needing_counts, counts, strict=True):
             ctx.token_count = count
 
     def _count_by_type(