[bug]: Header/top bar not responsive on mobile (overflows horizontally) — self-hosted v1.3.1

Note: This issue was researched and written by an AI assistant (Claude Code) on my behalf, and verified against a live self-hosted instance. — @jrbromberg

Describe the bug

On mobile (iOS, WebKit), the top bar of a project's Work Items view is not responsive. The workspace switcher + "Search commands…" field + the Work Items / Display / Analytics controls render at desktop widths and overflow horizontally past the viewport instead of collapsing into a mobile layout. The search field and right-side controls are cut off / require horizontal scrolling.

The issue list content itself loads and renders fine — this is specifically the header/top-bar layout on narrow screens.

Steps to reproduce

1. Self-host Plane CE v1.3.1.
2. Open a project's Work Items (issues) view in a mobile browser (iOS Safari/Chrome, ~390px wide).
3. Observe the top bar overflowing horizontally; controls extend beyond the screen edge.

Expected behavior

The header/top bar collapses responsively on narrow viewports (e.g. condensed controls or an overflow menu), staying within the viewport width.

Environment

• Plane: self-hosted Community Edition v1.3.1 (Docker Compose)
• Device/browser: iPhone, iOS 26 (WebKit — both Safari and iOS Chrome)
• Accessed over the network via a browser (not the native app)

Screenshot

Mobile view of the Work Items top bar — the "Search commands…" field and the Work Items / Display / Analytics controls overflow the ~390px viewport instead of collapsing.

Start by reproducing the Work Items view at roughly 390px width on a mobile browser, then trace the header/top-bar entry point and its workspace switcher, command search, and Work Items/Display/Analytics controls. Compare the layout at narrow and desktop widths; done means the complete top bar stays within the viewport without horizontal scrolling while its controls remain usable.