tui: sidebar overlaps vertical tabs and auto-hide has no effect

Summary

With vertical tabs enabled, the sidebar overlaps and covers the chat — the message list is obscured and can't be scrolled. Separately, the "sidebar auto hide" command has no visible effect in the TUI: after "hide sidebar" it never re-shows, and after "show sidebar" it never hides.

Environment

• opencode version: v0.0.0-next-17292
• OS: Windows_NT 10.0.26200 (win32 x64)
• Terminal: TERM=xterm-256color; TERM_PROGRAM/COLORTERM/WT_SESSION unset
• Shell: C:\Windows\system32\cmd.exe
• Install/channel: next
• Active plugins: opencode-mobile-use (TUI plugin tui.tsx provides a sidebar widget; server plugin provides phone_* tools)

Reproduction

Vertical tabs + sidebar overlap:

1. Enable vertical tabs (tabs.enabled: true, tabs.layout: "vertical" / tabs.vertical: true in cli.json).
2. Open the TUI with the sidebar visible.
3. Observe the chat pane alongside the vertical tab strip.

Sidebar auto-hide command:

1. In the TUI press Ctrl+P and run hide sidebar.
2. Run sidebar auto hide.
3. The sidebar stays hidden — auto-hide never brings it back.
4. Run show sidebar, then sidebar auto hide again.
5. The sidebar stays on screen permanently — auto-hide never hides it.

Expected Behavior

• Vertical tabs and the sidebar should lay out without the sidebar covering the chat; the chat should remain scrollable.
• The "sidebar auto hide" command should toggle auto-hide behavior: the sidebar hides when not in use and re-appears as needed, independent of the explicit show/hide toggle.

Actual Behavior

• The sidebar covers the chat content when vertical tabs are enabled; the chat cannot be scrolled up or down.
• The "sidebar auto hide" command appears to do nothing — sidebar visibility only ever changes via the explicit show/hide sidebar command.

Additional Context

• Screenshot attached showing the sidebar overlapping the chat with vertical tabs.
• Frequency: reproducible consistently in this setup.
• No workaround found: auto-hide cannot be made to work, and the overlap persists while vertical tabs are on.