test: Add comprehensive test coverage for Opus 4.5 aliases

Address review feedback:
- Add test for claude-opus alias in test_alias_resolution
- Add tests for anthropic/claude-opus-4.5 full name and opus4.5 alias
  in test_registry_capabilities

tests/test_openrouter_registry.py

@@ -90,6 +90,7 @@ class TestOpenRouterModelRegistry:
         test_cases = [
             ("opus", "anthropic/claude-opus-4.5"),  # opus now points to 4.5
             ("OPUS", "anthropic/claude-opus-4.5"),  # Case insensitive
+            ("claude-opus", "anthropic/claude-opus-4.5"),
             ("opus4.5", "anthropic/claude-opus-4.5"),
             ("opus4.1", "anthropic/claude-opus-4.1"),  # 4.1 still accessible
             ("sonnet", "anthropic/claude-sonnet-4.5"),