TUI shows wrong theme on startup when system dark/light mode changed since last session #21871

Bug Description

When launching the OpenCode TUI in iTerm2 (with automatic dark/light mode switching based on system appearance), the initial theme mode is incorrect.

Example: If I was in light mode last time I used OpenCode, but now my system is in dark mode, OpenCode still shows light mode on startup. However, if I toggle the system appearance after OpenCode is running, it correctly switches themes via the CliRenderEvents.THEME_MODE event.

Steps to Reproduce

1. Open OpenCode in dark mode → use it → exit
2. Switch system to light mode (or vice versa)
3. Reopen OpenCode → it still shows the previous session's theme instead of the current one

Root Cause

In packages/opencode/src/cli/cmd/tui/context/theme.tsx, the ThemeProvider init prioritizes the cached theme_mode from KV storage over the freshly detected mode from OSC 11 (props.mode):

setStore(
  produce((draft) => {
    const lock = pick(kv.get("theme_mode_lock"))
    const mode = pick(kv.get("theme_mode", props.mode))  // ← cached value takes priority
    draft.mode = lock ?? mode ?? props.mode
    // ...
  }),
)

Since apply() saves theme_mode to KV on every mode change, the stale cached value from the previous session overrides the current OSC 11 detection result on the next startup.

The runtime detection works fine because the renderer emits CliRenderEvents.THEME_MODE events which call apply() and update the mode correctly after startup.

Expected Behavior

When no theme_mode_lock is set, the startup mode should use the real-time OSC 11 detection result (props.mode), not the cached value from the previous session.

Suggested Fix

// In ThemeProvider init:
const lock = pick(kv.get("theme_mode_lock"))
// When not locked, always prefer the fresh OSC 11 detection result
draft.mode = lock ?? props.mode

The KV-cached theme_mode should only be used as a fallback when OSC 11 detection fails (returns no result), not as the primary source.

Environment

• OpenCode v1.4.3
• iTerm2 on macOS with automatic dark/light mode switching
• macOS appearance set to "Auto"