factor out compute_plot_group_id_v2() and expose it to python

[arvidn]

Note

Low Risk
Refactor-only extraction of existing v2 hashing with dedicated tests; compute_plot_id_v2 behavior is preserved via delegation.

Overview
v2 plot group ID is now a first-class helper: compute_plot_group_id_v2 implements sha256(strength + plot_pk + (pool_pk | contract_ph)), and compute_plot_id_v2 calls it before hashing plot_index and meta_group (same formula as before, just split).

Python bindings add compute_plot_group_id_v2 in the wheel (api.rs, module registration) with matching stubs in generate_type_stubs.py / chia_rs.pyi. New Rust regression tests cover pool-pk and contract-puzzle-hash variants for the group ID.

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[coveralls-official]

Coverage Report for CI Build 28596604212

Coverage decreased (-0.04%) to 81.484%

Details

• Coverage decreased (-0.04%) from the base build.
• Patch coverage: 13 uncovered changes across 2 files (14 of 27 lines covered, 51.85%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
wheel/src/api.rs	13	1	7.69%
crates/chia-protocol/src/proof_of_space.rs	14	13	92.86%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	18935
Covered Lines:	15429
Line Coverage:	81.48%
Coverage Strength:	11921444.41 hits per line

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💛 - Coveralls