Add PowerShell dev/test scripts and Windows-first README commands

scripts/dev.ps1

@@ -0,0 +1,13 @@
+# Builds the gateway binary (when missing) and starts the Tauri dev app.
+param([switch]$NoBuild)
+
+$ErrorActionPreference = "Stop"
+$repoRoot = Split-Path -Parent $PSScriptRoot
+Set-Location $repoRoot
+
+$gateway = Join-Path $repoRoot "bin\gateway.exe"
+if (-not $NoBuild -and -not (Test-Path $gateway)) {
+    & (Join-Path $PSScriptRoot "build-gateway.ps1")
+}
+
+npm run tauri dev

scripts/test.ps1

@@ -0,0 +1,13 @@
+# Runs the full test suite: Go tests, then frontend vitest.
+param([switch]$SkipFrontend)
+
+$ErrorActionPreference = "Stop"
+$repoRoot = Split-Path -Parent $PSScriptRoot
+Set-Location $repoRoot
+
+go test ./...
+if ($LASTEXITCODE -ne 0) { exit 1 }
+
+if (-not $SkipFrontend) {
+    npm test
+}