[Feature] Add ChatGPT timeline support with reference to chatgpt-gemini-timeline

需求描述 | Feature Description

Voyager currently provides timeline navigation for Gemini and Claude, but not for ChatGPT.

I am currently using houyanchao/chatgpt-gemini-timeline, whose ChatGPT timeline works well with long conversations. I would like to suggest adding an independent ChatGPT Timeline plugin to Voyager.

This proposal is not intended to replace or directly copy another extension. Thank you to the Voyager maintainers for the existing timeline and plugin architecture, and to the author of chatgpt-gemini-timeline for open-sourcing and maintaining its ChatGPT implementation.

解决方案 | Proposed Solution

Add a separate built-in plugin such as voyager.chatgpt-timeline:

• Reuse Voyager's existing timeline UI, preview panel and starred-message system.
• Implement a dedicated ChatGPT adapter for message detection, SPA navigation and long-conversation virtualization.
• Refer to the platform-adaptation ideas in houyanchao/chatgpt-gemini-timeline rather than importing its entire extension.
• Prefer a DOM-only MVP without network interception.
• If any source code is reused, preserve the original copyright, GPL license and attribution.

Reference project:

https://github.com/houyanchao/chatgpt-gemini-timeline

✅ 验收标准 | Acceptance Criteria

• After enabling the plugin on chatgpt.com, user messages appear as timeline nodes.
• Clicking a node scrolls to the corresponding message.
• It works after switching conversations and adding new messages.
• Long conversations and virtualized message nodes do not cause obvious ordering errors.
• Existing Voyager and ChatGPT functionality remains unaffected.
• Reused third-party code, if any, is clearly credited and license-compliant.

替代方案 | Alternatives Considered

Continue using Voyager and chatgpt-gemini-timeline as two separate extensions.

This works, but results in duplicated features, settings and page injections. A Voyager-native implementation would provide a more consistent experience.

补充信息 | Additional Information

Related: #259

This is a feature request rather than a bug report. I understand that the maintainers may decide that it is outside the current project scope.

Reference implementation:

https://github.com/houyanchao/chatgpt-gemini-timeline

A screenshot or short recording of its ChatGPT timeline can be attached here as a UI reference.

贡献意愿 | Contribution

• 我愿意为该功能贡献代码 / I am willing to contribute code for this feature
• 若 Issue 未标记 community-only，其他贡献者可评论 /claim 认领 / Other contributors may use /claim unless the issue is labeled community-only