Sidebar overlay dismissal persists hide preference, overlay z-index, and slash exact-match ranking

[A-x6]

Description

Three TUI bugs introduced with the sidebar overlay work in #89:

1. Dismissing the narrow-terminal sidebar overlay (Escape or clicking the backdrop) writes the persisted sidebar preference to "hide", so the sidebar never auto-appears again on wide terminals until manually toggled.
2. The home overlay renders without a z-index above the content pane and prompt (zIndex={1000}), so it paints underneath them and the backdrop doesn't receive clicks.
3. The slash-command autocomplete fuzzy-ranks an exact name match below longer commands, so typing /compact can select /compact-view instead of /compact.

Plugins

No response

OpenCode version

dev (bolt-cli)

Steps to reproduce

1. Shrink the terminal below the wide breakpoint, open the sidebar, dismiss it with Escape, then widen the terminal: the sidebar no longer auto-appears.
2. On home with a narrow terminal, open the sidebar overlay: it paints below the prompt and backdrop clicks don't dismiss it.
3. Type /compact in the prompt with both /compact and /compact-view registered: the exact match isn't selected first.

Screenshot and/or share link

No response

Operating System

any

Terminal

any