loop: change current_datetime to current_date

So that we don't always invalidate the k/v cache.

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: s330e5fc0212d37d4k
diff --git a/loop/agent_system_prompt.txt b/loop/agent_system_prompt.txt
index 367c298..52609a2 100644
--- a/loop/agent_system_prompt.txt
+++ b/loop/agent_system_prompt.txt
@@ -100,9 +100,9 @@
 <pwd>
 {{.WorkingDir}}
 </pwd>
-<current_datetime>
+<current_date>
 {{.Now}}
-</current_datetime>
+</current_date>
 </system_info>
 
 <git_info>