Fix/stale command hints

[lingyun14beta]

fix #8043
v4.23.0 移除了大量内置指令，但部分日志和配置提示仍引用了需安装扩展指令的插件/不存在的指令（/t2i、/switch、/wl、/tool off_all），改为引导用户使用 /new 或前往 WebUI 操作。

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Modifications / 改动点

• result_decorate/stage.py — /t2i → WebUI
• builtin_stars/astrbot/main.py — /switch → /new
• core/config/default.py — /wl → WebUI
• core/provider/sources/openai_source.py — /tool off_all → WebUI

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

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

这是一个日志改动）

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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

Bug Fixes:

• Correct stale log and configuration hints that referenced removed or unavailable commands for session switching, whitelisting, text-to-image, and tool disabling.

[sourcery-ai]

Hey - I've left some high level feedback:

• For the new WebUI guidance messages, consider adding more specific navigation paths (e.g., exact menu names or tabs) so users can quickly locate the relevant settings without guesswork.
• In openai_source.py, the case where the model does not support tools may be more of a user-actionable warning than a hard error; consider using logger.warning to better reflect severity and avoid alarming logs for expected misconfigurations.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- For the new WebUI guidance messages, consider adding more specific navigation paths (e.g., exact menu names or tabs) so users can quickly locate the relevant settings without guesswork.
- In `openai_source.py`, the case where the model does not support tools may be more of a user-actionable warning than a hard error; consider using `logger.warning` to better reflect severity and avoid alarming logs for expected misconfigurations.

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[gemini-code-assist]

Code Review

This pull request updates several user-facing log messages and configuration hints to guide users toward the WebUI instead of deprecated CLI commands. Feedback includes identifying dead code in openai_source.py due to a redundant error check and a recommendation to update internationalization files to ensure consistency across translations.