fix(scripts): stop check-prerequisites text mode crashing on a legacy stdout code page

[jawwad-ali]

Problem

_check_file / _check_dir in scripts/python/check_prerequisites.py hard-code the U+2713 / U+2717 glyphs and print() them to sys.stdout:

marker = "✓" if path.is_file() else "✗"
print(f"  {marker} {description}")

On Windows sys.stdout falls back to the ANSI code page whenever stdout is not a console — a pipe or a file redirect, which is exactly how an agent or a workflow step invokes these scripts. U+2713 is unencodable in cp1252.

Reproduction on current main (81bf741)

stdout encoding: cp1252
UnicodeEncodeError: 'charmap' codec can't encode character '✓' in position 2

Text mode therefore aborts right after printing AVAILABLE_DOCS:, so the caller gets a header with no document lines under it — and a non-zero exit for a repository that is perfectly healthy.

Fix

Downgrade to ASCII only when stdout cannot encode the glyph, so a UTF-8 console is unaffected:

glyph = "✓" if ok else "✗"
try:
    glyph.encode(getattr(sys.stdout, "encoding", None) or "utf-8")
except (LookupError, UnicodeEncodeError):
    return "[OK]" if ok else "[FAIL]"
return glyph

[OK] / [FAIL] is not invented — it is the ASCII rendering these markers already have in this repo:

Site	Code
scripts/powershell/common.ps1:243	Write-Output " [OK] $Description"
scripts/powershell/common.ps1:246	Write-Output " [FAIL] $Description"
tests/parity_helpers.py:130-131	text.replace(" ✓ ", " [OK] ").replace(" ✗ ", " [FAIL] ")

The PowerShell twin emits the ASCII form natively, and the parity helper maps the glyphs onto it — so the test suite already treats the two forms as equivalent output. Nothing downstream distinguishes them.

Breaking risk: a UTF-8-capable stdout still gets the glyphs, byte-identical to today. The only case that changes is one that previously raised and truncated the report. Callers parsing the marker are already required to accept both forms, per normalize_status_text.

Scope note

scripts/python/setup_tasks.py:58-65 carries a byte-identical block and crashes the same way. I kept this PR to one script — happy to extend it to the twin here or as a follow-up, whichever you prefer.

Verification

• Fail-before / pass-after: the new test (running the real script with PYTHONIOENCODING=cp1252) fails on unpatched src and passes with the fix. File: 1 failed → 12 passed, 8 skipped.
• Scoped regression: failure set identical to the clean-main baseline captured on 81bf741 (0 pre-existing in scope).
• uvx ruff@0.15.0 check src tests → clean

Note this test file is also touched by my open #3785 (a comment-only change to scripts/python/common.py), so expect a trivial append conflict if that merges first — happy to rebase.

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Written with assistance from Claude Code. Bug found, reproduced, and verified by me on current main.