set shell default to Rscript, and ensure package is installed before …

…using internal function

.github/workflows/R-CMD-check.yaml

@@ -10,6 +10,10 @@ on:
 
 name: R-CMD-check.yaml
 
+defaults:
+  run:
+    shell: Rscript {0}
+
 permissions: read-all
 
 jobs:
@@ -49,15 +53,16 @@ jobs:
           extra-packages: any::rcmdcheck
           needs: check
 
+      - name: Install package + deps
+        run: remotes::install_local(dependencies = TRUE, force = TRUE)
+
       - name: Install greta deps
         run: |
           library(greta)
           greta::install_greta_deps(timeout = 50)
-        shell: Rscript {0}
 
       - name: Situation Report on greta install
         run: greta::greta_sitrep()
-        shell: Rscript {0}
 
       - uses: r-lib/actions/check-r-package@v2
         with: