[Feature]: Add Copilot CLI support

### Platform

macOS

### Operating system version

macOS Sequoia 15.7.7 (24G720)

### System architecture

ARM64 (M1, M2, etc)

### PolyScope Version

0.19.0

### Bug description

Hi there,

we use Copilot and Copilot CLI (From GitHub) at work so I can't use Polyscope right now. Therefore my feature request is to add this to Polyscope.

As Copliot CLI gets more popular currently and the app already requires you to use GitHub, it would be great if we could use Polyscope with GitHub Copilot and the Copilot CLI.

### Steps to reproduce

- Install Copilot CLI
- Install Polyscope
- Start Polyscope
- Currently you get a message, that you have to install Claude Code, Cursor or Codex CLI

### Relevant log output

```shell

```

Install Copilot CLI on macOS, then start Polyscope and inspect how it detects Claude Code, Cursor, or Codex CLI. Identify the entry point that produces the installation message and trace the existing CLI integrations. Done means Polyscope recognizes GitHub Copilot CLI and no longer requires one of the currently supported tools.

Written by the indexing model from the issue text.