TUI system theme never refreshes terminal palette without a ?997 report (stale inside herdr)

Description

When OpenCode's TUI runs inside a terminal multiplexer that caches and replays the host terminal's color scheme (herdr), the system theme never re-detects the palette when the host appearance changes. The palette is only refreshed on a \e[?997 color-scheme report or SIGUSR2; there is no re-query on window focus or any manual refresh command.

Reproduced: with ~/.config/opencode/tui.json set to {"theme": "system"} inside herdr on macOS:

1. Host terminal dark → OpenCode system theme renders dark.
2. Host terminal switched to a light profile, Terminal window refocused.
3. OpenCode system theme stays dark indefinitely; no ?997 report arrives from the host (Terminal.app doesn't emit one) and nothing triggers a re-query.

The relevant code only refreshes on CliRenderEvents.THEME_MODE / the ?997 handler / SIGUSR2 (packages/tui/src/context/theme.tsx resolveSystemTheme/refreshSystemTheme, plus renderer.getPalette in packages/core/src/renderer.ts).

Plugins

None relevant. Running as opencode TUI inside herdr.

OpenCode version

1.18.18

Steps to reproduce

1. tui.json: { "theme": "system" }.
2. Run opencode inside a herdr pane with a dark host terminal; confirm dark system theme.
3. Switch the host terminal to a light profile and refocus the window.
4. Observe the system theme stays dark; it never refreshes.

Screenshot and/or share link

N/A

Operating System

macOS 26.5.2

Terminal

Terminal.app, inside herdr 0.8.0