feat: copy VS Code token to multiple providers

[christso]

Plan

1. generate config to prioritize providers to determine which token to copy first.
2. auto-discover tokens from VS Code, Codex etc.
3. copy tokens to destination providers using -o provider option (e.g. -o vscode).

CLI reference

# copy token from preferred provider to vscode
allagents mcp sync vscode

# copy token from codex to vscode
allagents mcp sync vscode -i codex

# setup universal workspace from plugin directory
allagents plugin install EntityProcess/allagents/plugins/agent-setup