fix: prevent install.ps1 from crashing PowerShell on error

When run via `irm ... | iex`, `exit` terminates the entire PowerShell
session. Wrapped the installer in a function and replaced all `exit`
calls with `return` so errors are reported cleanly without killing
the terminal.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

install.ps1

@@ -1,8 +1,7 @@
 # Transmute CLI installer for Windows
 # Usage: irm https://raw.githubusercontent.com/noauf/Transmute/main/install.ps1 | iex
 
-$ErrorActionPreference = "Stop"
-
+function Install-Transmute {
     $REPO = "noauf/Transmute"
     $BINARY = "transmute"
 
@@ -12,12 +11,11 @@ Write-Host "  ======================"
     Write-Host ""
 
     # Detect architecture
-$ARCH = if ([System.Environment]::Is64BitOperatingSystem) {
-    if ($env:PROCESSOR_ARCHITECTURE -eq "ARM64") { "arm64" } else { "x86_64" }
-} else {
+    if (-not [System.Environment]::Is64BitOperatingSystem) {
         Write-Host "  Error: 32-bit Windows is not supported" -ForegroundColor Red
-    exit 1
+        return
     }
+    $ARCH = if ($env:PROCESSOR_ARCHITECTURE -eq "ARM64") { "arm64" } else { "x86_64" }
 
     Write-Host "  OS:   windows"
     Write-Host "  Arch: $ARCH"
@@ -32,12 +30,12 @@ try {
         $TAG = $release.tag_name
     } catch {
         Write-Host "  Error: could not fetch latest release: $_" -ForegroundColor Red
-    exit 1
+        return
     }
 
     if (-not $TAG) {
         Write-Host "  Error: could not determine latest release" -ForegroundColor Red
-    exit 1
+        return
     }
 
     Write-Host "  Latest version: $TAG"
@@ -65,7 +63,7 @@ try {
 
         if (-not (Test-Path $EXE_SOURCE)) {
             Write-Host "  Error: could not find $EXE_NAME in archive" -ForegroundColor Red
-        exit 1
+            return
         }
 
         # Determine install directory
@@ -76,7 +74,7 @@ try {
         Copy-Item -Path $EXE_SOURCE -Destination $INSTALL_PATH -Force
 
         Write-Host ""
-    Write-Host "  Installed transmute $TAG to $INSTALL_PATH"
+        Write-Host "  Installed transmute $TAG to $INSTALL_PATH" -ForegroundColor Green
         Write-Host ""
 
         # Add to PATH if not already there
@@ -94,6 +92,11 @@ try {
         Write-Host "    transmute --help         Show all options"
         Write-Host ""
 
+    } catch {
+        Write-Host "  Error: $_" -ForegroundColor Red
     } finally {
         Remove-Item -Recurse -Force $TMP_DIR -ErrorAction SilentlyContinue
     }
+}
+
+Install-Transmute