Add ~/.agents/skills/ as a default skill discovery directory

[spboyer]

Problem

The GitHub Copilot for Azure (GHCP4A) VS Code extension installs skills to ~/.agents/skills/. This directory is automatically discovered by VS Code, but not by the Copilot CLI.

Currently, the Copilot CLI only discovers skills from:

• ~/.copilot/skills/ (user-level)
• .copilot/skills/ (project-level)
• Paths explicitly listed in skill_directories in ~/.copilot/config.json

This means skills installed by the VS Code extension (e.g., from microsoft/GitHub-Copilot-for-Azure) are invisible to the CLI unless users manually add ~/.agents/skills to their skill_directories config or create symlinks.

Current Workaround

Users must either:

1. Add "~/.agents/skills" to skill_directories in ~/.copilot/config.json
2. Create symlinks from ~/.copilot/skills/ → ~/.agents/skills/ for each skill

Proposal

Add ~/.agents/skills/ as a default skill discovery directory in the Copilot CLI, alongside the existing ~/.copilot/skills/. This would align CLI behavior with VS Code and ensure skills installed by extensions like GHCP4A are available across both surfaces without manual configuration.

As noted by Qianhao Dong:

The current GHCP4A extension installs skills to ~/.agents/skills, which is only discovered by VSC. Would it be better to use ~/.copilot/skills, which can be discovered by both VSC and Copilot CLI?

Either direction works — add ~/.agents/skills to CLI discovery, or have extensions install to ~/.copilot/skills — but the gap should be closed so skills are portable across Copilot surfaces.

Evidence

On a system with both VS Code + GHCP4A and Copilot CLI installed:

~/.agents/skills/          # 44 skills (installed by GHCP4A extension)
~/.copilot/skills/         # 25 skills (only 4 are symlinks to ~/.agents/skills/)

The vast majority of Azure skills are only available in VS Code today.

Implementation Note

The skill discovery logic likely lives in github/copilot-agent-runtime rather than this repo. The change would be to add ~/.agents/skills/ to the default skill directory search path alongside ~/.copilot/skills/.