fix(tool): enforce prompt Fix #200

[xiaobaicai66695]

What type of PR is this?

fix

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• The description of this PR title is user-oriented and clear enough for others to understand.
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(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:
Fix issue #200: In the human-in-the-loop/1_approval example, the Qwen model sometimes passed phone_number as a number instead of a string. This PR strengthens the agent's Instruction prompt to explicitly require string type for all fields, provide an example for phone number, and forbid number type. After the change, the Qwen model behaves correctly.

zh(optional): 修复 #200：在 human-in-the-loop/1_approval 示例中，Qwen 模型有时将 phone_number 作为数字而非字符串传递。此 PR 强化了 Agent 的 Instruction 提示词，明确要求所有字段为字符串类型，为电话号码提供示例，并禁止使用数字类型。修改后 Qwen 模型行为正确。

(Optional) Which issue(s) this PR fixes:

Fixes #200

(optional) The PR that updates user documentation:

N/A

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