Windows support: psmux hint, install.ps1, updated docs

install.ps1

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+# Install script for kctl-tui on Windows.
+# Downloads the latest GitHub release binary matching the current architecture
+# and installs it to your PATH.
+#
+# Usage (PowerShell):
+#   irm https://raw.githubusercontent.com/skoelle/kctl-tui/main/install.ps1 | iex
+#
+# Or save and run locally:
+#   .\install.ps1
+#
+# Requires: PowerShell 5.1+, internet access.
+
+$ErrorActionPreference = "Stop"
+
+$Repo = "skoelle/kctl-tui"
+$BinName = "kctl-tui"
+
+# --- Detect architecture ---
+$arch = $env:PROCESSOR_ARCHITECTURE
+switch ($arch) {
+    "AMD64"   { $goarch = "amd64" }
+    "ARM64"   { $goarch = "arm64" }
+    default {
+        Write-Error "Unsupported architecture: $arch"
+        exit 1
+    }
+}
+
+# --- Determine install directory ---
+$installDir = "$env:USERPROFILE\bin"
+if (-not (Test-Path $installDir)) {
+    New-Item -ItemType Directory -Path $installDir | Out-Null
+}
+
+# Add to PATH if not already there
+$currentPath = [Environment]::GetEnvironmentVariable("Path", "User")
+if ($currentPath -notlike "*$installDir*") {
+    [Environment]::SetEnvironmentVariable("Path", "$currentPath;$installDir", "User")
+    $env:Path = "$env:Path;$installDir"
+    Write-Host "Added $installDir to your PATH."
+}
+
+# --- Query GitHub API for latest release ---
+Write-Host "Detecting latest release for $Repo ..."
+try {
+    $release = Invoke-RestMethod -Uri "https://api.github.com/repos/$Repo/releases/latest" -UseBasicParsing
+} catch {
+    Write-Error "Failed to reach the GitHub API (network error). Check your internet connection and try again."
+    exit 1
+}
+
+$tag = $release.tag_name
+if (-not $tag) {
+    Write-Error "Could not find a published release for $Repo. No release has been tagged yet."
+    exit 1
+}
+
+Write-Host "Latest release: $tag"
+
+# --- Download binary ---
+$asset = "kctl-tui-windows-${goarch}.exe"
+$url = "https://github.com/$Repo/releases/download/$tag/$asset"
+$outFile = "$installDir\$BinName.exe"
+
+Write-Host "Downloading $asset ($tag) ..."
+try {
+    Invoke-WebRequest -Uri $url -OutFile $outFile -UseBasicParsing
+} catch {
+    Write-Error "Download failed: $_"
+    exit 1
+}
+
+Write-Host "Installed $BinName to $outFile"
+Write-Host "Done. Run '$BinName' to get started."