fix(anthropic-base): pass through top-level cache_control for automatic caching

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: bhuvansingla

src/providers/anthropic-base/messages.ts

@@ -48,6 +48,10 @@ export const messagesBaseConfig: ProviderConfig = {
     param: 'thinking',
     required: false,
   },
+  cache_control: {
+    param: 'cache_control',
+    required: false,
+  },
   tool_choice: {
     param: 'tool_choice',
     required: false,