feat: add shared Rust MSIX engine and CLI

Closes #2

src/scripts/Check.ps1

@@ -0,0 +1,32 @@
+param([string]$MakeAppx)
+$ErrorActionPreference = 'Stop'
+$sourceRoot = (Resolve-Path (Join-Path $PSScriptRoot '..')).Path
+function Check-Exit { if ($LASTEXITCODE -ne 0) { throw "Command failed: $LASTEXITCODE" } }
+Push-Location $sourceRoot
+try {
+    cargo fmt --all --check
+    Check-Exit
+    cargo test --locked --workspace
+    Check-Exit
+    if ($MakeAppx) {
+        $priorTool = $env:MSIX_TEST_MAKEAPPX
+        try {
+            $env:MSIX_TEST_MAKEAPPX = (Resolve-Path -LiteralPath $MakeAppx).Path
+            cargo test --locked -p package-infra --test workflow -- --ignored
+            Check-Exit
+        } finally { $env:MSIX_TEST_MAKEAPPX = $priorTool }
+    }
+    Push-Location apps/desktop
+    try {
+        npm.cmd ci
+        Check-Exit
+        npm.cmd run test
+        Check-Exit
+        npm.cmd run build
+        Check-Exit
+    } finally { Pop-Location }
+    cargo clippy --locked --workspace --all-targets -- -D warnings
+    Check-Exit
+    cargo build --locked -p msix-studio --features custom-protocol
+    Check-Exit
+} finally { Pop-Location }