ci: run the vpm scripts through bash

The nix runner has no /usr/bin/env, so the '#!/usr/bin/env bash' shebang
cannot resolve; invoke the scripts as arguments to bash instead.

.gitea/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
         run: nix build .#aac --print-build-logs
 
       - name: Package VPM zip
-        run: nix develop -c ./vpm/package.sh
+        run: nix develop -c bash ./vpm/package.sh
 
       - name: Build Unity bundle
         run: nix build .#default --print-build-logs

.gitea/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
         run: nix build .#aac --print-build-logs
 
       - name: Package VPM zip
-        run: nix develop -c ./vpm/package.sh
+        run: nix develop -c bash ./vpm/package.sh
 
       - name: Publish release and upload zip
         env:
@@ -26,7 +26,7 @@ jobs:
           SERVER: ${{ github.server_url }}
           REPO: ${{ github.repository }}
           TAG: ${{ github.ref_name }}
-        run: nix develop -c ./vpm/publish.sh
+        run: nix develop -c bash ./vpm/publish.sh
 
       # The index carries the zip's sha256, which only exists after packaging.
       - name: Commit updated VPM index