Add Dockerfile.test as reusable infrastructure for spinning up local
test instances with libsql (no PostgreSQL dependency). Defaults to
port 3003 to avoid conflict with dev server.
Add local-test workspace skill that teaches the agent how to build,
run, and test against local Docker containers using Chrome MCP browser
automation tools. Covers LLM backend configuration, multi-instance
testing, cleanup, and troubleshooting.
