bug: agents and prompts under .github folder not copied to target workspace

[christso]

This might not require code change and simply needs specifying the paths to copy in workspace.yaml
However, for simplicity, perhaps it's better to do this by default if .github / .claude / .codex folder is detected and the matching client is defined in workspace.yaml, e.g. if .copilot or .vscode is defined then we copy to .github/~.copilot folder (for project/user scope).

{plugin-name}/.github/prompts -> {workspace-folder}/.github/prompts.