Implement agent kit renderer

[jorisjonkers-dev-agents]

Summary

• port the renderer, manifest, templates, council bundle, and installer artifact into the root kit layout
• add manifest validation, renderer diagnostics, CI gates, and release tag configuration
• document the spec plan, task trace, render workflow, and portability contract

Validation

• python3 render-agent-kit.py --check
• python3 render-agent-kit.py --doctor
• python3 render-agent-kit.py --output
• scripts/validate_manifest.py
• ruff check .
• python3 -m compileall render-agent-kit.py scripts council
• bash syntax checks for installer and hook scripts
• installer dry-run, user install/uninstall, and project install smoke tests