[FEATURE]: Desktop: reserve a larger draggable region at the top edge of the window (hard to drag when many tabs are open)

Verified

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement

On macOS, the OpenCode desktop window hides the native title bar and renders its own top strip (titleBarStyle: "hidden", frame: false, ~40px tall). When several sessions/tabs are open, that top area is almost entirely covered by the tab bar, so the actually draggable region shrinks to a very thin sliver along the top edge. Grabbing the window to move it becomes impractical.

Please reserve a dedicated, reasonably tall draggable region at the top edge of the window (a -webkit-app-region: drag zone) that the tab bar does not occupy — for example a taller hit-area above/around the tabs, or making the empty margin around the tab row draggable.

Why it matters

Users routinely move a window by grabbing its title bar. With the current layout the draggable zone is so small that grabs often land on the interactive tab bar or miss entirely, forcing users to resize the window instead. This is especially noticeable with multiple tabs open, which is the default multi-session workflow of the app.

Environment

• OpenCode Desktop 1.18.16
• macOS 15.7.9