fix: mismatch in roundtrip

[stephantul]

We stored bytes but read them as non-bytes. This is fine for most code, since code is often just ASCII, but would crash on non-ascii

closes #167

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/semble/index/index.py	100.00% <100.00%> (ø)
src/semble/version.py	100.00% <100.00%> (ø)

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[greptile-apps]

Confidence Score: 5/5

Safe to merge — the change is a minimal, targeted correction of a read/write mode mismatch with no side effects.

The two-line fix directly aligns load_from_disk with save: both now use binary I/O, which is what orjson expects. No logic is altered, and orjson.loads already handles bytes input, so the roundtrip is now fully consistent for any content including non-ASCII.

No files require special attention.

_{Reviews (2): Last reviewed commit: "up version" | Re-trigger Greptile}