fix(studio): avoid UnicodeEncodeError on Windows cp1252 consoles (#4699)

* fix(studio): replace unicode emoji in print() to avoid cp1252 crash on Windows

On Windows the default console encoding is cp1252 which cannot encode
unicode emoji like U+2705 or U+26A0. bare print() calls with these
characters cause a UnicodeEncodeError at runtime.

- run.py: replace emoji with ASCII status prefixes [OK] and [WARNING]
- format_conversion.py: remove duplicate print() that mirrors the
  logger.info() call on the next line, and drop the emoji from the
  log message since loggers handle encoding separately

* fix(studio): apply same emoji/print cleanup to parallel VLM conversion path

The parallel URL-based conversion logic has the same duplicate print()
with emoji that was fixed in the sequential path. Remove the bare
print() and drop the emoji from the logger.info() call.

* Treat install_python_stack.py failure as fatal in setup.ps1

On Linux/Mac, setup.sh runs under set -euo pipefail so a non-zero
exit from install_python_stack.py aborts the installer. On Windows,
setup.ps1 had no exit code check -- if the Python script crashed
(eg from the cp1252 UnicodeEncodeError), the installer silently
continued past the dependency loop and reported success. Studio
would then fail at launch with ModuleNotFoundError for structlog,
fastapi, and other deps that were never installed.

Capture $LASTEXITCODE and exit 1 if the dependency installer fails,
matching the error handling pattern already used for PyTorch install.

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

studio/backend/run.py

@@ -312,10 +312,10 @@ def run_server(
     if frontend_path:
         if setup_frontend(app, frontend_path):
             if not silent:
-                print(f"✅ Frontend loaded from {frontend_path}")
+                print(f"[OK] Frontend loaded from {frontend_path}")
         else:
             if not silent:
-                print(f"⚠️ Frontend not found at {frontend_path}")
+                print(f"[WARNING] Frontend not found at {frontend_path}")
 
     # Create the uvicorn server and expose it for signal handlers
     config = uvicorn.Config(

studio/backend/utils/datasets/format_conversion.py

@@ -553,13 +553,9 @@ def convert_to_vlm_format(
                         batch_results[idx] = future.result()
                     except Exception as e:
                         failed_count += 1
-                        if failed_count == 1:
-                            print(
-                                f"⚠️ First VLM conversion failure: {type(e).__name__}: {e}"
-                            )
                         if failed_count == 1:
                             logger.info(
-                                f"⚠️ First VLM conversion failure: {type(e).__name__}: {e}"
+                                f"First VLM conversion failure: {type(e).__name__}: {e}"
                             )
 
             converted_list.extend(r for r in batch_results if r is not None)
@@ -583,13 +579,10 @@ def convert_to_vlm_format(
                 converted_list.append(_convert_single_sample(sample))
             except Exception as e:
                 failed_count += 1
-                if failed_count == 1:
-                    # Log the first failure to aid debugging
-                    print(f"⚠️ First VLM conversion failure: {type(e).__name__}: {e}")
                 if failed_count == 1:
                     # Log the first failure to aid debugging
                     logger.info(
-                        f"⚠️ First VLM conversion failure: {type(e).__name__}: {e}"
+                        f"First VLM conversion failure: {type(e).__name__}: {e}"
                     )
             pbar.set_postfix(ok = len(converted_list), failed = failed_count, refresh = False)
         pbar.close()

studio/setup.ps1

@@ -1522,8 +1522,14 @@ if ($CuTag -eq "cpu") {
 # Ordered heavy dependency installation -- shared cross-platform script
 substep "running ordered dependency installation..."
 python "$PSScriptRoot\install_python_stack.py"
+$stackExit = $LASTEXITCODE
 # Restore ErrorActionPreference after pip/python work
 $ErrorActionPreference = $prevEAP
+if ($stackExit -ne 0) {
+    Write-Host "[FAILED] Python dependency installation failed (exit code $stackExit)" -ForegroundColor Red
+    Write-Host "   Re-run the installer or check the error above for details." -ForegroundColor Red
+    exit 1
+}
 
 # ── Pre-install transformers 5.x into .venv_t5/ ──
 # Models like GLM-4.7-Flash need transformers>=5.3.0. Instead of pip-installing