npm run build --prefix ./packages/borsh

The underlying problem was not the guest wrapper itself.

Two clean-environment issues were involved:

the root package-lock.json was stale relative to package.json
several package-level config files were still tracked as git symlink entries

This was masked on local Windows checkouts, where those files could appear usable, but it broke in clean Linux CI checkouts.

Verified

After this update, the PR no longer fails at the package build bootstrap stage:

Install Dependencies passes
Build borsh passes
Build SDK Core passes
Remaining CI status

The workflow still fails in the Check step, but that is now aligned with the existing repository state on master.

This PR has removed the PR-specific clean-checkout regression.
The remaining red status is the pre-existing repo-wide test failure already present on master, not a new failure introduced by the guest SDK changes.

Scope kept intentionally small

This PR does not:

redesign SDK architecture
add wallet-linking
add progression/rating
expand guest concepts beyond sdk-facade
attempt to repair unrelated legacy test failures already affecting master