Thanks for the contribution! A few things are needed before this can be reviewed:

1. Before/After Screenshots (required)

Per CONTRIBUTING.md:

For UI or UX changes, before/after images are required. PRs that change the interface or interaction flow without before/after images will likely be ignored, or closed in a regular maintainer sweep without review.

Please add screenshots showing the sidebar in its normal (expanded) state and the collapsed state.

2. Missing PR Description Sections

CONTRIBUTING.md specifies these sections for every PR:

• Thinking Path — why you approached it this way
• Why It Matters — the user problem this solves
• Verification — what you tested and how
• Risks / Follow-ups — edge cases, known tradeoffs, anything left open
• Model Used — if AI helped produce this change, list the provider and model name; if not, write None — human-authored

The current description covers What Changed well, but the above sections are missing.

Once those are added, we can move forward with a full review.

@aronprins — tagging you for UX review on this one.

This is a sidebar collapse toggle for desktop. The PR is currently on hold pending screenshots (requested above) and the missing PR description sections (Thinking Path, Why It Matters, Verification, Risks, Model Used).

Once @sheng-di adds those, your blessing on the UX approach would be great before we proceed with full review.

Screenshots

Before (sidebar expanded — master branch)

After (sidebar collapsed — this PR)

How it works:

• New Toggle sidebar button added at the bottom of the rail nav (just above Settings)
• Click to collapse/expand the left sidebar with a smooth CSS transition
• Keyboard shortcut: Ctrl+B (Cmd+B on macOS)
• State persists across sessions via localStorage

Screenshots

Before (sidebar expanded — master branch)

After (sidebar collapsed — this PR)

How it works:

• New Toggle sidebar button added at the bottom of the rail nav (just above Settings)
• Click to collapse/expand the left sidebar with a smooth CSS transition
• Keyboard shortcut: Ctrl+B (Cmd+B on macOS)
• State persists across sessions via localStorage

None of your "after" screenshots work? They work but i mean what is in the screenshots looks broken?

Updated Screenshots

重新截图，CSS 完整加载，两张都是干净的状态：

Before（侧边栏展开）

After（侧边栏折叠）

Hold — awaiting explicit @aronprins UX approval

Thanks for the updated screenshots, @sheng-di! The implementation looks clean.

Per our UX review process: @aronprins quoted the screenshots but hasn't posted an explicit approval comment yet. @aronprins — please post an "LGTM" or "Approved" comment here when you're happy with the sidebar collapse UX. We'll move to technical review immediately after.

The screenshots showing the collapsed/expanded states look good — just need the explicit sign-off to proceed.

@nesquena what do you think? I personally think its not needed.

Hold — UX feedback is negative; feature unlikely to merge in current form

@sheng-di — @aronprins reviewed the screenshots and commented: "I personally think it's not needed."

Since this is a UX-affecting feature (sidebar collapse toggle on desktop), we need positive UX buy-in before landing it. @aronprins's position is that the current layout doesn't need a collapse toggle.

Path forward: If you believe there's a strong user case for this, please:

1. Share specific user feedback or a concrete use case where the sidebar collapse is needed
2. Propose an alternative approach (e.g., draggable resize rather than collapse)

Otherwise, this PR will remain on hold. Thank you for the effort — the implementation itself is clean!

@nesquena what do you think? I personally think its not needed.

I'll go with your idea for now, but when I accessed this site using my iPad, I found the conversation area to be quite small and inconvenient to use. If we only focus on the desktop version now, it's not really necessary since the screen is wide, but it will still be very important if we plan to expand to a mobile version later.