Skill sync: bulk reconcile registry with platforms

[devrimcavusoglu]

Context

Currently, installing skills is one-skill-one-platform-at-a-time. A skill sync command could reconcile state in bulk: install new, update changed, optionally remove stale.

Idea

Add skern skill sync to sync all skills from the registry to all detected platforms in one shot.

Open Questions — Decisions Needed

The value of a blanket sync is unclear given the project's strategic direction:

1. Dynamic skill loading vs bulk sync — The intended model is that agents dynamically install/uninstall skills as needed, keeping only the required skills at a platform's registry at any given time. A bulk sync contradicts this by pushing everything at once. Which model takes priority, or do both coexist?

2. Batch install/uninstall as an alternative — Rather than full sync, batch operations (skern skill install skill-a skill-b --platform all) may better serve the dynamic loading model. An agent could install multiple skills in one call without syncing everything.

3. Sync semantics — If sync is implemented, what happens with:

   • Skills installed on a platform but not in the registry (remove? ignore?)
   • Skills that were manually edited on the platform side (overwrite? skip? warn?)
   • Scope handling (sync user scope, project scope, or both?)

4. Relationship to --force on install (Add --force flag to skill install for overwrite #33) — Does sync implicitly force-overwrite, or does it respect existing installations?

These questions need resolution before implementation can proceed.

References

Analysis item 2.2

[devrimcavusoglu]

Related: #52 explores dynamic skill loading (the finer-grained alternative to bulk sync discussed in this issue).