fix: Add caching by default for deepseek coder.

aider/models.py

@@ -75,6 +75,7 @@ class ModelSettings:
     extra_headers: Optional[dict] = None
     max_tokens: Optional[int] = None
     cache_control: bool = False
+    caches_by_default: bool = False
 
 
 # https://platform.openai.com/docs/models/gpt-4-and-gpt-4-turbo
@@ -400,6 +401,7 @@ MODEL_SETTINGS = [
         send_undo_reply=True,
         examples_as_sys_msg=True,
         reminder="sys",
+        caches_by_default=True,
     ),
     ModelSettings(
         "openrouter/deepseek/deepseek-coder",