Contribute local entities to a git registry directly from the project

[AlexPagnotta]

Future idea, not scheduled yet.

Problem

Registries only flow one way. From a project you can registry pull entities down into .harness/src/, but there's no way to send a local entity back up to the registry.

So sharing a skill (or hook, subagent, etc.) you built in a project means doing it by hand: clone the registry repo, recreate the entity in its layout, commit, open a PR, then come back and pull to re-sync.

Goal

One command to contribute a local entity to the registry, without manually cloning or crafting a PR:

harness registry push skill my-skill

It would take the local source, write it into the registry layout, and publish it. Basically the reverse of pull.

Possible approaches

• Push a branch — clone, copy the entity in, commit and push. Simplest, reuses the existing clone/auth code. No review step.
• Open a PR — same as above but opens a PR for review. Nicer, but needs the gh CLI or GitHub API (GitHub-only).
• Generate a patch — write the files and output a patch for the user to submit. Lowest risk, but manual.