chore(ci): bump socket-registry action refs to main (6147a08c)

[jdalton]

Summary

• Bump socket-registry action refs to 6147a08c (sfw-free shim support)
• Remove inline pnpm alias/shim blocks (now handled by shared install action)

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Note

Medium Risk
Updates shared GitHub Action references and removes local pnpm shims, which could affect CI/publish behavior if the new action revision handles setup differently.

Overview
Updates CI and release workflows to use SocketDev install/git-signing actions pinned to 6147a08c.

Removes the inline pnpm alias/SFW shim logic from ci.yml, provenance.yml, and weekly-update.yml, relying on the shared install action to provide the correct pnpm wrapper/setup.

^{Reviewed by Cursor Bugbot for commit 36e34bc. Configure here.}