Copy/Paste broken in Copilot CLI when using SSH inside a tmux session on macOS/Linux → Windows Server 2025

### Describe the bug

After upgrading to Copilot CLI v1.0.47, copy/paste no longer works when accessing Copilot CLI on a remote Windows Server 2025 machine via SSH **from inside a tmux session**.

### Affected version

v1.0.47

### Steps to reproduce the behavior

| Scenario | Copy/Paste |
|---|---|
| Open Copilot CLI directly on macOS/Linux | ✅ Works |
| SSH into Windows Server, open Copilot CLI | ✅ Works |
| Open tmux session → SSH into Windows Server → open Copilot CLI | ❌ Broken |

Other CLI tools (Codex CLI, Gemini CLI) handle copy/paste correctly in all three scenarios.

## tmux Configuration

```
set -g prefix C-a
unbind C-b

bind C-a send-prefix
bind | split-window -h -c "#{pane_current_path}"
bind - split-window -v -c "#{pane_current_path}"
unbind '"'
unbind %

set -g mouse on
set -g history-limit 50000
set -g allow-passthrough on

set -g default-terminal "tmux-256color"
set -as terminal-features ",xterm*:RGB"

bind r source-file ~/.tmux.conf \; display "Reloaded!"

set -g @plugin 'tmux-plugins/tpm'
set -g @plugin 'tmux-plugins/tmux-sensible'

set -g @plugin 'egel/tmux-gruvbox'
set -g @tmux-gruvbox 'light'
set -g @tmux-gruvbox-statusbar-alpha 'true'

set -g @plugin 'tmux-plugins/tmux-resurrect'
set -g @plugin 'tmux-plugins/tmux-continuum'
set -g @continuum-restore 'on'
set -g @resurrect-capture-pane-contents 'on'

run '~/.tmux/plugins/tpm/tpm'

set -g status-right ''
```

### Expected behavior

Copy/paste should work consistently regardless of whether the terminal is running inside a tmux session.

### Additional context

The `set -g allow-passthrough on` option is already set in the tmux config, which is typically required for OSC52 clipboard passthrough. This suggests Copilot CLI may be using a different clipboard mechanism that does not survive the `tmux → SSH` chain.

まず、issue にある 3 つのシナリオ、特に tmux → SSH → Copilot CLI を、提供された tmux 設定を使って再現します。CLI のコピー/ペースト動作を追跡し、期待される OSC52 passthrough 経路と比較します。macOS/Linux から tmux と SSH を経由して Windows Server 2025 に接続した場合に、直接の場合を壊すことなく、コピーとペーストが一貫して動作すれば完了です。

索引モデルが issue の本文から書いたものです。