Add developer-setup skill to installer output

[interworks-morr]

Summary

The installer should drop the /interworks:developer-setup Claude Code skill file onto the user's machine during installation. This skill handles everything the installer can't: GitHub CLI, Python, GitHub account setup, org membership, pre-commit/gitleaks, and global CLAUDE.md.

What to do

Copy the SKILL.md file from InterWorks/claude-plugins to:

~/.claude/skills/interworks-setup/SKILL.md

This path is relative to the user's home directory (e.g. C:\Users\<username>\.claude\skills\interworks-setup\SKILL.md on Windows).

Why

The installer currently handles Git, Node.js, VS Code, and Claude Code itself. But new staff also need:

• GitHub CLI (gh)
• Python (via pyenv)
• A GitHub account authenticated and added to the InterWorks org
• Pre-commit with gitleaks for secret scanning
• The global ~/.claude/CLAUDE.md guardrails file
• Connection to the InterWorks plugin marketplace

The developer-setup skill walks them through all of this interactively via Claude Code. It needs to be delivered by the installer because it's the bootstrap skill — users don't have GitHub org access yet, so they can't get it from the plugin marketplace.

Source of truth

The canonical copy of this skill lives at:
https://github.com/InterWorks/claude-plugins/blob/main/plugins/interworks/skills/developer-setup/SKILL.md

After installation, the user runs /interworks:developer-setup in Claude Code to complete their environment setup.