[OpenSpec] Bundle related skills into a packaged skill structure

The OpenSpec change lifecycle is currently exposed as ~10 separate skills (new, apply, verify, archive, etc.), even though they all belong to the same domain. Proposal: consolidate them into a single, simply named openspec skill that internally routes to the appropriate action (apply, continue, archive, ff, etc.). This follows the same idea as the packaged approach used in Vercel’s react-best-practice skill: https://github.com/vercel-labs/agent-skills/tree/main/skills/react-best-practice --- There’s another small issue: some skills reference or instruct users to run commands like 'run /opsx:apply'. In this setup, that’s redundant and potentially confusing. Skills already inject the required context and behavior when invoked. Since the logic was moved from AGENTS.md into skills, references should point to the skill itself, not to a command. In practice, in Claude /skill works the same way as /opsx, so mentioning commands here doesn’t add value.