fix: make runtime boot animation archives deterministic

[0cwa]

Failure found by finished-OTA verification

The force-publish after PR #110 successfully:

• installed both /media/bootanimation.zip and /media/bootanimation-dark.zip;
• repacked and AVB-signed product.img;
• created the patched OTA.

Publication was correctly blocked only because the finished-OTA verifier rebuilt the expected runtime ZIP later and got different bytes.

The reason is Python ZipFile.writestr(filename, ...): when passed only a filename, it stamps the new ZIP entry with the current time. The adapter therefore claimed to produce a deterministic runtime archive but did not.

Fix

Canonicalize every runtime ZIP entry with:

• fixed DOS epoch timestamp 1980-01-01 00:00:00;
• ZIP_STORED;
• Unix creator metadata;
• regular-file mode 0644;
• no extra field or comment.

This makes the runtime animation byte-for-byte reproducible regardless of source ZIP timestamps or the time the build/verifier runs.

Regression coverage

Two source animations with identical contents but different entry timestamps must now produce identical runtime ZIP bytes. Tests also require the canonical timestamp and stored compression.

The selection contract is bumped to product-image-root-theme-context-deterministic-stored-v7 so previous artifacts cannot satisfy existing-build preflight.

[coderabbitai]

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