feat: squads init creates .agents/idp/ with catalog template

[kokevidaurre]

What

squads init should create .agents/idp/catalog/ with a starter service entry so new users get IDP from day 1.

After init, squads catalog list should show their project as a service.

Expected behavior

squads init
# creates .agents/idp/catalog/<project-name>.yaml with:
# - name derived from git remote or directory name
# - type: product (if package.json exists) or domain
# - stack: detected from package.json/requirements.txt/go.mod
# - owner: default squad name
# - scorecard: product or domain

squads catalog list
# shows the service

Acceptance criteria

• squads init creates .agents/idp/catalog/<name>.yaml
• Service name auto-detected from git remote or directory
• Stack auto-detected from project files
• squads catalog list works after init
• Existing .agents/idp/ is not overwritten