Colors are completely off in tmux

### Describe the bug

When having a light theme, Copilot CLI light theme's colors are completely wrong when running in tmux. Outside tmux, everything's fine.

tmux vs regular shell:

The problem isn't just the aesthetics, some text is genuinely unreadable (like bright yellow on light background in the screenshot above).

### Affected version

GitHub Copilot CLI 1.0.61

### Steps to reproduce the behavior

- Set a light terminal theme
- Set the theme to "light" or "auto" in Copilot CLI
- Spawn the command menu with "/"

### Expected behavior

Exactly the same color in and outside tmux.

### Additional context

Env:
- WSL2, NixOS
- Terminal emulator: Windows Terminal
- Fish shell

In tmux:
```shell
❯ echo TERM=$TERM; tput colors
TERM=tmux-direct
16777216

❯ echo $COLORTERM
truecolor
```

Relevant tmux config:
```
# Enable true color support
set-option -as terminal-features ',*:RGB'
set -ga update-environment "COLORTERM"
set -ga update-environment "COLORFGBG"
set-environment -g COLORTERM "truecolor"
```

Issue #4212 seems related but I'm not sure if it's exactly the same. There is also issue #135 but it hasn't received any attention in months.

Riproduci la discrepanza dei colori del tema chiaro con Copilot CLI 1.0.61 dentro e fuori da tmux, seguendo la configurazione indicata di WSL2, NixOS, Windows Terminal e Fish. Inizia confrontando i valori dell’ambiente e la configurazione di tmux con issue #4212 e issue #135. Il lavoro è completato quando il tema chiaro o automatico visualizza gli stessi colori leggibili all’apertura del menu dei comandi con "/" dentro e fuori da tmux.

Scritto dal modello di indicizzazione a partire dal testo della issue.