ci: use the repo-local antelope core instead of a global install

[Upd4ting]

Summary

Remove the pnpm add --global @antelopejs/core step from the CI workflow. @antelopejs/core (^1.9.1) is already a devDependency, and pnpm test runs ajs module test . through a package.json script, so pnpm resolves ajs from node_modules/.bin. The global install was redundant and could mask a missing or mismatched local core.

Related issue

N/A — part of the org-wide cleanup removing the global antelope core install from CI workflows.

Verification

Ran every CI step locally, in order, on Node 24 with PATH stripped of any global ajs (command -v ajs returned nothing; inside pnpm scripts it resolved to ./node_modules/.bin/ajs):

• pnpm install --frozen-lockfile
• pnpm prepack
• pnpm lint (warnings only, no errors)
• pnpm format:check
• pnpm knip
• pnpm test — 83 passing

CI on this pull request validates the same steps without the global install.

Checklist

• The pull request title follows Conventional Commits.
• I added or updated tests when behavior changed. (N/A — CI-only change)
• I updated documentation when users or contributors are affected. (N/A)
• I documented breaking changes and migration steps. (N/A — no breaking changes)
• I did not include credentials or unrelated changes.