Bug: UnicodeEncodeError in create_provider_plugin.py on Windows (cp1252 console)

Describe the overall issue and situation

On Windows, scripts/create_provider_plugin.py and the test_plugin.py it generates print Unicode checkmarks (✓ / ✅). Windows consoles default stdout/stderr to a legacy code page (typically cp1252), so both scripts crash with UnicodeEncodeError before the plugin can be generated or verified.

This is the same root-cause class as #108, #158, and #166 (Windows cp1252 vs Unicode), which were fixed for file I/O / HTML export in io.py. The generator script's console output was not covered.

Related to #158 (6 ; already-fixed HTML/file I/O case). This issue is the remaining console-output path.

Expected behavior

python scripts/create_provider_plugin.py ... and the generated test_plugin.py print status lines successfully on a default Windows console.

Actual behavior

UnicodeEncodeError: 'charmap' codec can't encode character '\u2713' in position 0: character maps to <undefined>

pytest tests/create_provider_plugin_test.py also fails on Windows because subprocess.run(..., text=True) decodes the generated script's UTF-8 output with the locale encoding, producing mojibake instead of the expected checkmarks.

Steps to reproduce the issue

1. On Windows, open a default cmd.exe or PowerShell session (code page 1252 / cp1252).
2. From a clone: python scripts/create_provider_plugin.py --help or run the generator as documented.
3. Observe UnicodeEncodeError when the script prints a ✓ / ✅ status line.
4. Alternatively: pytest tests/create_provider_plugin_test.py — 15 failures on Windows before a UTF-8 stdout/stderr reconfigure.

Any additional content

• OS: Windows
• Python: 3.14 (also reproduces on other Windows CPython versions with a non-UTF-8 console)
• Fix proposed in https://github.com/google/langextract/pull/514 (reconfigure stdout/stderr to UTF-8; decode subprocess output as UTF-8)
• Environment: default Windows console, not Windows Terminal UTF-8 mode