feat(core,tooling): Windows support — shell selection, install.ps1, win-x64 release package, Windows CI (#79)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/landing/public/install.ps1

@@ -0,0 +1,33 @@
+# https://penguin.ooo/install.ps1 - PenguinHarness installer entry point for Windows.
+#
+# GitHub Pages cannot serve HTTP redirects, so this thin forwarder IS the
+# stable install URL: it fetches the real installer attached to the latest
+# GitHub release and runs it, forwarding every argument it was given. Usage:
+#
+#   irm https://penguin.ooo/install.ps1 | iex
+#   & ([scriptblock]::Create((irm https://penguin.ooo/install.ps1))) -Version v0.2.0
+#
+$ErrorActionPreference = "Stop"
+$ProgressPreference = "SilentlyContinue"
+try {
+  [Net.ServicePointManager]::SecurityProtocol = [Net.ServicePointManager]::SecurityProtocol -bor [Net.SecurityProtocolType]::Tls12
+} catch {
+  # .NET builds where the enum is immutable already default to TLS 1.2+.
+}
+# Download fully first, then run: executing a piped stream directly would run a
+# truncated download line by line, and the real installer moves the old
+# bin/lib/web/node aside before moving the new ones in - a cut connection
+# mid-way must never leave a half-executed installer. The installer runs as an
+# in-memory script block (not a script file): script files are subject to the
+# execution policy, which is Restricted by default on client Windows - while the
+# user has already consented to remote code by piping this forwarder into iex.
+# Neither this forwarder nor the installer calls `exit`, which in iex/script-block
+# context would terminate the user's whole PowerShell session.
+$Tmp = Join-Path ([IO.Path]::GetTempPath()) "penguin-install-$PID.ps1"
+try {
+  Invoke-WebRequest -Uri "https://github.com/Prism-Shadow/penguin-harness/releases/latest/download/install.ps1" -OutFile $Tmp -UseBasicParsing
+  $Installer = [scriptblock]::Create((Get-Content -Path $Tmp -Raw))
+  & $Installer @args
+} finally {
+  Remove-Item -Force $Tmp -ErrorAction SilentlyContinue
+}