fix(agenticark): preserve raw reasoning content from Ark Responses API

[N3kox]

What type of PR is this?

fix

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• This PR title match the format: (optional scope):
• The description of this PR title is user-oriented and clear enough for others to understand.
• No user documentation update is required because this fixes existing response conversion behavior without introducing a new public API.

(Optional) Translate the PR title into Chinese.

fix(agenticark): 保留 Ark Responses API 返回的原始思维链内容

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:

Ark Responses API can return raw reasoning content in reasoning.content when thinking summary compression is disabled. Previously, agenticark only converted reasoning.summary, causing the raw reasoning content to be dropped.

This PR:

• upgrades the Volcengine Go SDK to support reasoning.content and raw reasoning stream events;
• preserves raw reasoning content in schema.Reasoning.OpenAIExtension.Content;
• preserves encrypted reasoning content and supports passing raw reasoning back in subsequent requests;
• handles raw reasoning content in both streaming and non-streaming responses;
• adds regression tests based on the reported skip-thinking-summary response.

zh(optional):

当关闭思维链摘要压缩时，Ark Responses API 会通过 reasoning.content 返回原始思维链。此前 agenticark 仅转换 reasoning.summary，导致原始思维链内容丢失。

本 PR：

• 升级 Volcengine Go SDK，以支持 reasoning.content 和原始思维链流式事件；
• 将原始思维链保留至 schema.Reasoning.OpenAIExtension.Content；
• 保留加密思维链内容，并支持在后续请求中回传原始思维链；
• 同时兼容流式和非流式响应；
• 基于用户反馈的 skip-thinking-summary 响应补充回归测试。

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

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(optional) The PR that updates user documentation:

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[github-actions]

Need to create a new tag

The following modules have changes and may need version updates:

• components/model/agenticark (Current: components/model/agenticark/v0.2.4)

⚠️ Please create and push new version tags for these modules after merging this PR.

[github-actions]

Need to create a new tag

The following modules have changes and may need version updates:

• components/model/agenticark (Current: components/model/agenticark/v0.2.4)

⚠️ Please create and push new version tags for these modules after merging this PR.

[github-actions]

Need to create a new tag

The following modules have changes and may need version updates:

• components/model/agenticark (Current: components/model/agenticark/v0.2.4)

• components/model/ark (Current: components/model/ark/v0.1.69)

⚠️ Please create and push new version tags for these modules after merging this PR.

[github-actions]

Need to create a new tag

The following modules have changes and may need version updates:

• components/model/agenticark (Current: components/model/agenticark/v0.2.4)

• components/model/ark (Current: components/model/ark/v0.1.69)

⚠️ Please create and push new version tags for these modules after merging this PR.