PR: Windows Setup Improvements (#4299)

* quiet llama.cpp build, smarter CUDA install via winget, accept Python 3.11-3.13

* studio: hide Python traceback when setup script exits with error

* setup.ps1: auto-add Python Scripts dir to PATH so 'unsloth' command works in new terminals

* setup.ps1: fix GPU check to run nvidia-smi instead of just checking command existence

* setup.ps1: fix PATH check to use exact entry comparison instead of substring match

* setup.ps1: validate Python probe exit code before persisting Scripts PATH

cli/commands/studio.py

@@ -145,9 +145,11 @@ def setup():
         raise typer.Exit(1)
 
     if platform.system() == "Windows":
-        subprocess.run(
+        result = subprocess.run(
             ["powershell", "-ExecutionPolicy", "Bypass", "-File", str(script)],
-            check = True,
         )
     else:
-        subprocess.run(["bash", str(script)], check = True)
+        result = subprocess.run(["bash", str(script)])
+
+    if result.returncode != 0:
+        raise typer.Exit(result.returncode)