Fix Nix workflow bootstrap

Co-authored-by: dichhead <330471626+dichhead@users.noreply.github.com>

.github/workflows/weekly-release.yml

@@ -25,9 +25,6 @@ jobs:
   prepare:
     if: github.ref == 'refs/heads/main'
     runs-on: ubuntu-22.04
-    defaults:
-      run:
-        shell: 'nix develop --command bash --noprofile --norc -euo pipefail {0}'
     outputs:
       ready: ${{ steps.release.outputs.ready }}
       tag: ${{ steps.release.outputs.tag }}
@@ -39,18 +36,20 @@ jobs:
           fetch-depth: 0
       - uses: ./.github/actions/setup-nix
       - name: Validate release automation
-        run: python3 scripts/test_release.py
+        run: nix develop --command python3 scripts/test_release.py
       - name: Prepare release and verify published notes
         id: release
         env:
           GH_TOKEN: ${{ github.token }}
           PUBLISH: ${{ github.event_name == 'schedule' || inputs.publish }}
         run: |
+          nix develop --command bash --noprofile --norc -euo pipefail <<'EOF'
           if [ "$PUBLISH" = true ]; then
             python3 scripts/release.py prepare --publish
           else
             python3 scripts/release.py prepare
           fi
+          EOF
 
   # GITHUB_TOKEN releases do not trigger release events, so call both builds.
   web: