Terminal does not answer OSC 10/11 default-color queries, breaking light-background TUI detection (Codex input box renders dark on light theme)

## Environment

Orca v1.4.180, Windows, light terminal theme (Builtin Tango Light)

## Steps to reproduce

1. Set Orca terminal theme to a LIGHT theme.
2. Launch Codex TUI (`codex`) in an Orca terminal.
3. Observe the composer/input box is painted dark, clashing with the light background.

## Root cause

- Codex (Windows) probes terminal default colors via OSC 10/11 (`ESC ] 10;?` / `ESC ] 11;?`) with a 100ms startup timeout (`codex-rs/tui/src/terminal_probe.rs`, `DEFAULT_TIMEOUT`).
- Orca's xterm.js terminal never answers OSC 10/11 queries (no handler in the shipped bundle).
- Codex then falls back to `GetConsoleScreenBufferInfoEx`, which reads the conhost/conpty color table. Orca's light theme only affects the xterm.js render layer and is NOT synced to the conpty palette, so Codex sees the default dark background and paints the input box dark.
- TERM/COLORTERM are irrelevant on Codex's Windows path; `tui.theme` only affects syntax highlighting (openai/codex#21130), not the composer.

## Expected

Orca's terminal should answer OSC 10/11 queries with the active theme's background color (standard behavior in VS Code terminal / Windows Terminal / xterm).

## Suggested fix

Implement OSC 10/11 query responses in the terminal layer, returning the current terminal theme's default fg/bg colors.