checkpoint ProofOfSpace patch

[arvidn]

make parsing of ProofOfSpace more strict and less maleable, like the original Option<> parsing

Original PR against release/0.45.1: #1474

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Note

Medium Risk
Changes consensus-relevant proof serialization parsing; behavior shifts for malformed prefix bytes while intended valid encodings should stay compatible.

Overview
Tightens ProofOfSpace wire parsing by deriving version from the packed optional prefix as prefix >> 1 instead of treating only bit 1 as a boolean, so encodings with garbage high bits map to invalid versions and fail like stricter Option<>-style prefixes.

Expands unit coverage with helpers for building proofs and locating the prefix byte, plus roundtrip, parse_rejects, and high_prefix_bits_rejected cases for legacy v0 lenient pool/contract combinations, v1 XOR pool-vs-contract rules, unknown versions, and stable re-serialization.

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[coveralls-official]

Coverage Report for CI Build 28453872876

Coverage increased (+0.02%) to 81.527%

Details

• Coverage increased (+0.02%) from the base build.
• Patch coverage: 20 of 20 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	18914
Covered Lines:	15420
Line Coverage:	81.53%
Coverage Strength:	11936490.6 hits per line

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💛 - Coveralls