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/exceptions.py

@@ -61,7 +61,7 @@ class BudgetExceededError(ContextError):
             requested: Tokens requested
             context_type: Type of context that exceeded budget
         """
-        details = {
+        details: dict[str, Any] = {
             "allocated": allocated,
             "requested": requested,
             "overage": requested - allocated,
@@ -170,7 +170,7 @@ class AssemblyTimeoutError(ContextError):
             elapsed_ms: Actual elapsed time in milliseconds
             stage: Pipeline stage where timeout occurred
         """
-        details = {
+        details: dict[str, Any] = {
             "timeout_ms": timeout_ms,
             "elapsed_ms": round(elapsed_ms, 2),
         }