fix: make helper output safe on non-UTF-8 consoles

[motodriver]

Summary

• configure stdout as UTF-8 with replacement in the four affected helper entry points
• preserve the existing progress glyphs without crashing redirected non-UTF-8 streams
• add a regression test using an ASCII-configured redirected stdout

Validation

• python3 -m unittest discover -s tests -v (17 tests passed)
• python3 -m py_compile helpers/render.py helpers/grade.py helpers/pack_transcripts.py helpers/transcribe_batch.py tests/test_stdout_encoding.py
• git diff --check

AI assistance disclosure

TRAE assisted with issue analysis, implementation, regression-test drafting, and an independent P0-P2 review of this change. The human author reviewed the final diff and ran the validation commands listed above.

Closes #125

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Summary by cubic

Fixes helper scripts crashing on non-UTF-8 consoles by reconfiguring stdout to UTF-8 with replacement. Redirected output now shows progress glyphs instead of failing.

• Adds a regression test for ASCII-configured redirected stdout.

Closes #125.

^{Written for commit 28abe48. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 5 files

<sub>Reply with feedback, questions, or to request a fix.

Fix all with cubic | Re-trigger cubic</sub>

[motodriver]

Addressed both review findings in ef03684:

• extracted the shared stdout configuration into helpers/_util.py
• parameterized the ASCII redirected-stream regression across pack_transcripts, render, grade, and transcribe_batch

Validation:

• python3 -m unittest discover -s tests -v — 17 passed
• python3 -m py_compile helpers/_util.py helpers/render.py helpers/grade.py helpers/pack_transcripts.py helpers/transcribe_batch.py tests/test_stdout_encoding.py — passed
• git diff --check — passed

[cubic-dev-ai]

All reported issues were addressed across 6 files (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Fix all with cubic | Re-trigger cubic</sub>

[motodriver]

Addressed the latest P2 review finding in 28abe48.

The regression now executes each helper's actual CLI entry point with --help under PYTHONIOENCODING=ascii, then emits a Unicode probe from an atexit callback. This makes the test fail if any helper's main() stops calling configure_stdout().

Validation:

• python3 -m unittest tests.test_stdout_encoding -v — 1 passed
• python3 -m unittest discover -s tests -v — 17 passed
• python3 -m py_compile helpers/_util.py helpers/render.py helpers/grade.py helpers/pack_transcripts.py helpers/transcribe_batch.py tests/test_stdout_encoding.py — passed
• git diff --check — passed