fix: enable xAI Responses native web search

[wcqqq1214]

Fixes #9723.

This PR restores the xAI native-search toggle for openai_responses provider sources, injects the web_search tool into Responses API requests, and surfaces xAI url_citation sources as WebChat source cards.

Modifications / 改动点

• Expose the xAI native-search toggle for openai_responses provider sources and keep it disabled by default.

• Backfill the disabled toggle in the Dashboard when editing existing xAI provider sources that predate the setting.

• Add xAI's web_search tool to both streaming and non-streaming Responses API requests when the toggle is enabled, while preserving AstrBot function tools.

• Extract xAI url_citation annotations into LLMResponse.web_search_sources and carry them through the agent runner into the WebChat refs pipeline (chat / live-chat / OpenAPI consumers), rendering them as the existing clickable source cards.

• Update the English and Chinese configuration hints to describe xAI native Web Search rather than the legacy Chat Completions-only behavior.

• This is NOT a breaking change. / 这不是一个破坏性变更。

Verification Steps / 验证步骤

1. Ran Ruff lint and format checks for the changed Python files.
2. Built the Dashboard successfully, including vue-tsc --noEmit.
3. Started an isolated AstrBot instance and opened the real Dashboard in a browser.
4. Verified that an existing xAI provider source without xai_native_search displays the toggle as disabled by default; enabled it, saved it, reloaded the page, and confirmed the setting persisted.
5. Validated both streaming and non-streaming requests through OpenCode Go's Responses-compatible endpoint using grok-4.5, without an official xAI API key. The outgoing payload included {"type":"web_search"}, and the model returned current news with a source URL.
6. Repeated the final end-to-end Dashboard chat flow using the configured grok-4.5 model and received a current international-news result with a source URL.
7. Validated citation rendering against a local mock of the official xAI Responses web-search shape (web_search_call + url_citation): the sources were parsed and shown as WebChat source cards in both streaming and non-streaming paths.

Screenshots or Test Results / 运行截图或测试结果

1. Dashboard configuration

2. End-to-end WebChat result

This request uses Grok's native web_search tool through the Responses API. No AstrBot web-search plugin, function tool, or external search provider was configured.

3. Citation card via a local mock of the official xAI Responses shape

The mock returns the official xAI web_search_call + url_citation shape. Because OpenCode Go strips citation metadata, the source-card rendering is validated against the mock rather than a live provider; an official xAI API re-check is recommended.

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Checklist / 检查清单

• 😊 If there are new features added in the PR, I have discussed it with the authors through issues/emails, etc.
  / 如果 PR 中有新加入的功能，已经通过 Issue / 邮件等方式和作者讨论过。

• 👀 My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
  / 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。

• 🤓 I have ensured that no new dependencies are introduced, OR if new dependencies are introduced, they have been added to the appropriate locations in requirements.txt and pyproject.toml.
  / 我确保没有引入新依赖库，或者引入了新依赖库的同时将其添加到 requirements.txt 和 pyproject.toml 文件相应位置。

• 😮 My changes do not introduce malicious code.
  / 我的更改没有引入恶意代码。

Summary by Sourcery

Enable optional xAI native Web Search in Responses API requests and surface its citations throughout WebChat.

New Features:

• Enable optional native xAI Web Search for Responses API provider sources.
• Expose xAI citation URLs as clickable WebChat source cards across chat, live-chat, and OpenAPI consumers.

Bug Fixes:

• Restore the xAI native-search setting for Responses API sources and default it safely for existing configurations.

Enhancements:

• Preserve existing AstrBot function tools alongside the native xAI search tool and propagate structured search references through agent responses.

Documentation:

• Update English and Chinese configuration guidance to describe xAI native Web Search.

Tests:

• Update provider template coverage for the default xAI native-search setting.

[sourcery-ai]

Hey - I've reviewed your changes and they look great!

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[wcqqq1214]

@sourcery-ai review

[sourcery-ai]

Hey - I've left some high level feedback:

• In _query/_query_stream, tool_choice is only set when function tools are present, so xAI-native web_search alone will not get an explicit tool_choice; consider whether you want to force tool_choice='auto' whenever any tools (including web_search) are sent.
• Handling of the web_search_sources chain type is currently scattered across chat_service, live_chat_service, open_api_service, and astr_agent_run_util; consider centralizing this parsing/forwarding logic to a shared helper to reduce duplication and keep behavior consistent across channels.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `_query`/`_query_stream`, `tool_choice` is only set when function tools are present, so xAI-native `web_search` alone will not get an explicit `tool_choice`; consider whether you want to force `tool_choice='auto'` whenever any tools (including `web_search`) are sent.
- Handling of the `web_search_sources` chain type is currently scattered across `chat_service`, `live_chat_service`, `open_api_service`, and `astr_agent_run_util`; consider centralizing this parsing/forwarding logic to a shared helper to reduce duplication and keep behavior consistent across channels.

---

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