Remove duplicated skills and add agent-workflow install

[jdelfino]

Remove duplicated skills, commands, and AGENTS.md from devcontainer-template. Replace with agent-workflow installation.

Repo: jdelfino/devcontainer-template

Files to remove

• template/.claude/skills/ (entire directory — 8 skills)
• template/.claude/commands/ (entire directory — 5 commands)
• template/AGENTS.md.jinja
• AGENTS.md (root level)

Files to modify

• template/.devcontainer/post-create.sh: Add agent-workflow installer curl command
• template/.claude/settings.json: Remove beads MCP server, update permissions
• README.md: Reference agent-workflow for workflow setup