Add iex-compatible branch parsing

Remove the param block and rename DefaultBranch to $defaultBranch. Add argument parsing for iex-compatible invocations (e.g. `iex -dev main`, `iex main`, or no args) by inspecting $args and selecting the branch accordingly, then log the chosen branch. Simplify branch handling and build the GitHub ZIP download URL using the resolved branch. Small cleanup and reordering of steps to accommodate the new parsing logic.

Author: gnh1201

bootstrap.ps1

@@ -7,15 +7,11 @@
 #   irm https://catswords.blob.core.windows.net/welsonjs/bootstrap.ps1 | iex
 #   irm https://catswords.blob.core.windows.net/welsonjs/bootstrap.ps1 | iex -dev main
 #   irm https://catswords.blob.core.windows.net/welsonjs/bootstrap.ps1 | iex -dev dev
+#   irm https://catswords.blob.core.windows.net/welsonjs/bootstrap.ps1 | iex main
 # 
 # Central default branch configuration for this install script.
 # Update this value if the repository's default branch changes.
-$DefaultBranch = "master"
-
-param(
-    # Branch to install from; defaults to the repository's configured primary branch.
-    [string]$dev = $DefaultBranch
-)
+$defaultBranch = "master"
 
 $ErrorActionPreference = "Stop"
 
@@ -32,6 +28,27 @@ function Write-Err($msg) {
 }
 
 try {
+    # Step 0: Parse arguments (iex-compatible)
+    # Supports:
+    #   iex -dev main
+    #   iex main
+    #   iex
+    $branch = $defaultBranch
+
+    for ($i = 0; $i -lt $args.Count; $i++) {
+        $arg = $args[$i]
+
+        if ($arg -eq "-dev" -and ($i + 1) -lt $args.Count) {
+            $branch = $args[$i + 1]
+            break
+        }
+        elseif ($arg -notmatch "^-") {
+            $branch = $arg
+        }
+    }
+
+    Write-Step "Using branch: $branch"
+
     # Step 1: Create a temporary working directory using a UUID
     Write-Step "Creating temporary workspace..."
 
@@ -45,12 +62,7 @@ try {
     $repo = "gnh1201/welsonjs"
     $zipPath = Join-Path $tempDir "package.zip"
 
-    # Step 2: Determine branch (default: master)
-    $branch = $dev
-
-    Write-Step "Using branch: $branch"
-
-    # GitHub branch ZIP URL
+    # Step 2: Build download URL
     $downloadUrl = "https://github.com/$repo/archive/refs/heads/$branch.zip"
 
     Write-Ok "Download URL: $downloadUrl"
@@ -102,4 +114,4 @@ try {
 catch {
     Write-Err $_
     exit 1
-}
+}