chore: add extensions/@pgpm/* to pnpm workspace, remove CI workaround

The @pgpm/services dependency is already declared in
extensions/@pgpm/metaschema-modules/package.json. Adding the
extensions to the pnpm workspace means pnpm install resolves
it automatically — no need for a separate pgpm install step in CI.

Author: pyramation

.github/workflows/test-module-loader.yaml

@@ -53,9 +53,6 @@ jobs:
       - name: Bootstrap pgpm admin users
         run: pgpm admin-users bootstrap --yes
 
-      - name: Install pgpm module dependencies
-        run: cd extensions/@pgpm/metaschema-modules && pgpm install @pgpm/services
-
       - name: Generate function packages
         run: node --experimental-strip-types scripts/generate.ts