Read translation optimization source tests as UTF-8

[tianmind-studio]

Summary

• Read transcribe.py and translation_coordinator.py source snapshots as UTF-8 in test_translation_optimization.py.
• Fix Windows non-UTF-8 locale failures in the translation persistence guard source tests.
• Keep the existing translation optimization assertions unchanged.

Windows reproduction

Before this change on Windows with the default GBK locale:

• python -m pytest tests\unit\test_translation_optimization.py -q -> 2 failed, 90 passed
• failures were UnicodeDecodeError: 'gbk' codec can't decode byte ... while reading routers/transcribe.py and utils/translation_coordinator.py

Testing

• python -m pytest tests\unit\test_translation_optimization.py -q -> 92 passed
• python -m black --line-length 120 --skip-string-normalization tests\unit\test_translation_optimization.py --check
• python -m py_compile tests\unit\test_translation_optimization.py
• git diff --check origin/main...HEAD

[greptile-apps]

Greptile Summary

This PR adds encoding='utf-8' to three open() calls in test_translation_optimization.py that read Python source files (routers/transcribe.py and utils/translation_coordinator.py) as text. Without this, the tests would fail with UnicodeDecodeError on Windows systems whose default locale uses a non-UTF-8 codec (e.g., GBK).

• Adds encoding='utf-8' to all three open() calls that read source files in TestTranslateSegmentGuardWired, fixing Windows locale failures.
• No test logic or assertions are changed — this is a pure compatibility fix.

Confidence Score: 5/5

Safe to merge — the change is a three-line encoding fix in a test file with no impact on production code.

The change exclusively adds encoding='utf-8' to file-read calls in tests. All three relevant open() calls in the file now carry the explicit encoding; no test logic or assertions were altered. The fix is portable and correct.

No files require special attention.

Important Files Changed

Filename	Overview
backend/tests/unit/test_translation_optimization.py	Adds encoding='utf-8' to all three source-file open() calls in TestTranslateSegmentGuardWired; no other logic changes.

_{Reviews (1): Last reviewed commit: "Read translation optimization source tes..." | Re-trigger Greptile}