fix(core): clarify user-executed shell history (#37515)

Co-authored-by: Aiden Cline <rekram1-node@users.noreply.github.com>

packages/core/test/session-runner-message.test.ts

@@ -124,7 +124,12 @@ describe("toLLMMessages", () => {
     )
     expect(messages.slice(2).map((message) => message.content)).toEqual([
       [{ type: "text", text: "Synthetic context" }],
-      [{ type: "text", text: "Shell command: pwd\n\n/project" }],
+      [
+        {
+          type: "text",
+          text: "The following shell command was executed by the user:\n\nCommand:\npwd\n\nOutput:\n/project",
+        },
+      ],
       [
         {
           type: "text",