Allow agents-cli setup to target specific coding agents

[ftnext]

What is your feature suggestion?

Add an option to agents-cli setup to target specific coding agents, for example --agent codex or --agent claude-code.

Currently agents-cli setup appears to run npx skills add ... --all, which installs skills into every supported agent directory. Since npx skills already supports --agent/-a, it would be helpful if agents-cli setup exposed that option and passed it through.

% uvx google-agents-cli setup --workspace
% ls -a
.			.claude			.factory		.kode			.pochi			.windsurf
..			.codebuddy		.goose			.mcpjam			.qoder			.zencoder
.adal			.commandcode		.iflow			.mux			.qwen			skills
.agents			.continue		.junie			.neovate		.roo			skills-lock.json
.augment		.cortex			.kilocode		.openhands		.trae
.bob			.crush			.kiro			.pi			.vibe

What will this enable you to do?

I use only one coding agent in a given workspace, but agents-cli setup --workspace creates many agent-specific directories such as .claude, .windsurf, .qwen, .roo, etc.

Being able to choose the target agent would keep the workspace cleaner and avoid creating unused files/directories.

Additional context

Example desired usage:

agents-cli setup --workspace --agent codex

This could translate internally to something like:

npx -y skills@1.4.8 add <source> --skill '*' --agent codex -y