move shared agent skills out of @proofkit/typegen

[eluce2]

Problem

We currently ship the onboarding/typegen AgentSkills from @proofkit/typegen.

That made more sense when typegen was expected to be installed directly in a consuming project, but we now prefer typegen to be run via npx @proofkit/typegen so users get the latest version more reliably.

That creates an awkward packaging mismatch:

• a project may install @proofkit/fmdapi, @proofkit/fmodata, or both
• the project may not install @proofkit/typegen directly
• but the agent guidance for getting started / typegen setup is currently packaged under packages/typegen/skills

Goal

Move the shared AgentSkills that are relevant across ProofKit packages out of @proofkit/typegen and into a shared location/package that can be shipped with @proofkit/fmdapi and @proofkit/fmodata.

Proposed direction

• create a shared skills package or shared skills location in the monorepo
• move these skills out of packages/typegen/skills:
  • getting-started
  • typegen-setup
• make those shared skills available when installing:
  • @proofkit/fmdapi
  • @proofkit/fmodata
• avoid requiring direct installation of @proofkit/typegen just to expose those skills to agents

Why

This keeps the preferred CLI UX:

npx @proofkit/typegen

while still making the relevant skills discoverable in repos that only install the runtime packages.

Notes

This is intentionally separate from the dependency discussion in #200. Even if we accept the npx-reliability fix there, we should still clean up where these shared skills live.