[Bugfix] Assign original prompt back to RequestOutput

[yuanheng-zhao]

PLEASE FILL IN THE PR DESCRIPTION HERE ENSURING ALL CHECKLIST ITEMS (AT THE BOTTOM) HAVE BEEN CONSIDERED.

Purpose

Resolves #2497

Test Plan

Ming e2e example test (any e2e test printing out RequestOutput.prompt

Test Result

Before this fix:

Prompt:
None
Text Output:
<think>
Okay, let's try to figure out

After

Prompt:
<role>SYSTEM</role>你是一个友好的AI助手。

detailed thinking on<|role_end|><role>HUMAN</role><IMAGE>Based on the following rules:
•       You control the smiley face character
•       You can move up, down, left, and right, and only a single square at a time
•       Walls are dark grey and cannot be moved into
•       The brown square is a box
•       The box can be pushed by moving into it (i.e., if you are in the square adjacent to the box to the left, and move onto the square with the box, the box will move one square to the right).
•       The box cannot be pushed into walls
•       The blue door at the bottom is locked and cannot be passed through, unless the box is placed on the blue square
•       The square beneath the blue door is the exit
•       Moving from one square to another

Let's assume a coordinate system where the smiley face is on the top left at (1,1) and the square below it is (1,2). The smiley face performs the following moves: {down, right, right, right}, such that the smiley face is at square (4,2) and the box is in square (5,2). What are the next sequence of moves that must be done to move the box down to (5,3)? Give your answer as a comma separated list.<|role_end|><role>ASSISTANT</role>
Text Output:
<think>
Okay, let's try to figure out the

---

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
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[princepride]

LGTM