startup: /b runs a script, as --script does

Shortcuts written for other CAD programs pass the startup script as
`/b script.scr`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.rs

@@ -27,7 +27,14 @@ fn main() -> iced::Result {
     #[cfg(not(target_arch = "wasm32"))]
     {
         use clap::Parser;
-        let args = cli::Cli::parse();
+        // `/b script.scr`, the startup switch shortcuts carry, is `--script`.
+        let args = cli::Cli::parse_from(std::env::args_os().map(|arg| {
+            if arg == "/b" || arg == "/B" {
+                "--script".into()
+            } else {
+                arg
+            }
+        }));
 
         // GPU probe child: exercise one backend offscreen, print one JSON
         // line on success and exit 0/1. This must run before any logging/GUI