[CHIA-4279] parse ProofOfSpace

[arvidn]

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

---

Note

High Risk
Changes consensus-relevant ProofOfSpace deserialization; stricter parsing could reject previously accepted (malleable) encodings on the wire.

Overview
Tightens ProofOfSpace wire parsing so the packed pool_contract prefix byte is interpreted like a normal Option<> prefix (only bits 0–1 are meaningful), reducing malleability on the network.

Parse change: version is derived with prefix >> 1 instead of treating only bit 1 as a boolean. Non-canonical prefixes that set higher bits now surface as unknown versions and fail with InvalidPoS, rather than being accepted as v0/v1 with altered optional semantics.

Tests: Adds helpers and expands coverage for serialize/parse round-trips (v0 lenient pool/contract combinations, v1 size collapsing to 0), explicit rejections (v1 must have exactly one of pool pk vs contract, unknown version on serialize), and regression that bits 2–7 on the prefix byte are rejected for both versions.

^{Reviewed by Cursor Bugbot for commit 3a65f0e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coveralls-official]

Coverage Report for CI Build 28447616578

Warning

No base build found for commit de5c8b3 on release/0.45.1.
Coverage changes can't be calculated without a base build.
If a base build is processing, this comment will update automatically when it completes.

Coverage: 80.971%

Details

• Patch coverage: 20 of 20 lines across 1 file are fully covered (100%).

Uncovered Changes

No uncovered changes found.

Coverage Regressions

Requires a base build to compare against. How to fix this →

---

Coverage Stats

Relevant Lines:	18603
Covered Lines:	15063
Line Coverage:	80.97%
Coverage Strength:	12135899.61 hits per line

---

💛 - Coveralls