feat(context): enhance timeout handling, tenant isolation, and budget management

- Added timeout enforcement for token counting, scoring, and compression with detailed error handling.
- Introduced tenant isolation in context caching using project and agent identifiers.
- Enhanced budget management with stricter checks for critical context overspending and buffer limitations.
- Optimized per-context locking with cleanup to prevent memory leaks in concurrent environments.
- Updated default assembly timeout settings for improved performance and reliability.
- Improved XML escaping in Claude adapter for safety against injection attacks.
- Standardized token estimation using model-specific ratios.

backend/tests/services/context/test_config.py

@@ -72,7 +72,7 @@ class TestContextSettings:
         """Test performance settings."""
         settings = ContextSettings()
 
-        assert settings.max_assembly_time_ms == 100
+        assert settings.max_assembly_time_ms == 2000
         assert settings.parallel_scoring is True
         assert settings.max_parallel_scores == 10