fix(ci): fix test-vp-setup-exe workflow syntax error

Replace dynamic matrix.shell in shell: field with explicit shell values
per step. The matrix.shell expression was not recognized by the GitHub
Actions YAML parser when used in the shell: context. Use a single job
that verifies installation from pwsh, cmd, and bash sequentially.

Author: fengmk2

.github/workflows/test-standalone-install.yml

@@ -630,14 +630,10 @@ jobs:
           which vp
 
   test-vp-setup-exe:
-    name: Test vp-setup.exe (${{ matrix.shell }})
+    name: Test vp-setup.exe (pwsh)
     runs-on: windows-latest
     permissions:
       contents: read
-    strategy:
-      fail-fast: false
-      matrix:
-        shell: [cmd, pwsh, bash]
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: oxc-project/setup-rust@23f38cfb0c04af97a055f76acee94d5be71c7c82 # v1.0.16
@@ -647,7 +643,7 @@ jobs:
         run: cargo build --release -p vite_installer
 
       - name: Install via vp-setup.exe (silent)
-        shell: ${{ matrix.shell }}
+        shell: pwsh
         run: ./target/release/vp-setup.exe -y
         env:
           VP_VERSION: alpha
@@ -657,7 +653,19 @@ jobs:
         run: echo "$USERPROFILE/.vite-plus/bin" >> $GITHUB_PATH
 
       - name: Verify installation
-        shell: ${{ matrix.shell }}
+        shell: pwsh
+        run: |
+          vp --version
+          vp --help
+
+      - name: Verify installation (cmd)
+        shell: cmd
+        run: |
+          vp --version
+          vp --help
+
+      - name: Verify installation (bash)
+        shell: bash
         run: |
           vp --version
           vp --help