feat: update action.yml to use pwsh shell and enhance vm.py with start option; add credential management scripts

.gitea/actions/local-ci-build/action.yml

@@ -208,7 +208,7 @@ runs:
     # ── Invoke the CI orchestrator ─────────────────────────────────────────────
     - name: Invoke CI Job
       id: invoke-ci
-      shell: powershell
+      shell: pwsh
       # Inputs are forwarded via environment variables to avoid shell injection
       # from user-supplied build-command or path strings.
       env:
@@ -374,7 +374,7 @@ runs:
     # directly (see build-nsInnoUnp.yml release job).
     - name: Report artifact location
       if: success() && inputs.skip-artifact != 'true'
-      shell: powershell
+      shell: pwsh
       run: |
         $p = '${{ steps.invoke-ci.outputs.artifact-path }}'
         if (-not (Test-Path -LiteralPath $p) -or
@@ -387,7 +387,7 @@ runs:
 
     - name: Report diagnostic log location on failure
       if: failure()
-      shell: powershell
+      shell: pwsh
       run: |
         $p = '${{ steps.invoke-ci.outputs.artifact-path }}'
         if ($p -and (Test-Path -LiteralPath $p)) {