Fix Windows release job: WebView2 step used CMD syntax under PowerShell shell

[Copilot]

The Download and extract WebView2 runtime step in build_and_release.yml failed on windows-latest because it had no explicit shell: set, defaulting to pwsh, while its commands (mkdir, rmdir /s /q) were written for cmd. PowerShell rejected rmdir /s /q ext with A positional parameter cannot be found that accepts argument '/q', breaking the release build.

Changes

• Set shell: pwsh explicitly on the step to remove ambiguity about which shell executes it.
• Replaced CMD-specific commands with their PowerShell equivalents:
  • cd → Set-Location
  • mkdir → New-Item -ItemType Directory -Force
  • move → Move-Item -Force
  • rmdir /s /q → Remove-Item -Recurse -Force
  • del → Remove-Item -Force

- name: Download and extract WebView2 runtime
  shell: pwsh
  run: |
    Set-Location build\bin
    curl -o webview2.nupkg -L "https://globalcdn.nuget.org/packages/webview2.runtime.${{ matrix.wv2arch }}.151.0.4129.107.nupkg?packageVersion=151.0.4129.107"
    New-Item -ItemType Directory -Force -Path internals\bin | Out-Null
    7z x webview2.nupkg -oext -y
    Move-Item -Force ext\contentFiles\any\any\WebView2 internals\bin\WebView2
    Remove-Item -Recurse -Force ext
    Remove-Item -Force webview2.nupkg

Other steps in the workflow relying on mkdir/cd were left untouched since those are valid PowerShell aliases and don't error out; only rmdir /s /q used CMD-only flags. Packaging behavior (download, extract, move into internals\bin\WebView2, cleanup) is unchanged.