test(grey-state): add proptests for accumulate sub-transition

[wangzishuai1987]

Summary

Adds property-based tests for the accumulate sub-transition's pure functions (Section 12):

decode_preimage_info_timeslots:

• Roundtrip: encode → decode returns original timeslots
• No-panic: arbitrary bytes never cause panic

compute_dependencies:

• No duplicates in dependency set
• All prerequisites appear in dependencies

partition_reports:

• Total count invariant: |immediate| + |queued| == |reports|
• No-dependency reports are always immediate
• Dependency-bearing reports are always queued

edit_queue:

• No accumulated entries survive editing
• No accumulated dependencies survive editing

resolve_queue:

• Empty queue yields nothing
• All resolved reports have corresponding records

find_free_service_id:

• Result is not in the existing accounts map
• Result is above the S threshold

encode_accumulate_args:

• Always produces exactly 12 bytes
• Deterministic encoding

compute_output_hash:

• Deterministic and order-independent
• Sensitive to any entry change

Refs: #229

[github-actions]

Genesis Review

Comparison targets:

• 6d050e34 (6d050e3)
• 2bc664b9 (2bc664b)
• b7aa7e80 (b7aa7e8)
• 835adfee (835adfe)
• bf816b61 (bf816b6)
• 84b39d09 (84b39d0)
• f2d141e0 (f2d141e)

How to review

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/review
difficulty: <commit1>, <commit2>, ..., <commitN>, currentPR
novelty: <commit1>, <commit2>, ..., <commitN>, currentPR
design: <commit1>, <commit2>, ..., <commitN>, currentPR
verdict: merge

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[johandroid]

/review
difficulty: 6d050e3, 835adfe, currentPR, 2bc664b, bf816b6, 84b39d0, b7aa7e8, f2d141e
novelty: 6d050e3, 835adfe, currentPR, 2bc664b, b7aa7e8, bf816b6, 84b39d0, f2d141e
design: 6d050e3, 835adfe, 2bc664b, currentPR, bf816b6, 84b39d0, b7aa7e8, f2d141e
verdict: merge

Adds broad property coverage for accumulate queue/dependency helpers, service ID selection, argument encoding, and output hash determinism/order independence. It ranks below the GRANDPA persistence fix and interpreter dispatch refactor, but above smaller state/type/doc coverage because accumulate has a larger behavioral surface. Merge is reasonable as targeted state-transition test coverage.

[github-actions]

JAR Bot: Review recorded from @johandroid (1 reviews, 0 meta-reviews).
Merge weight: 0/37665 (need >50%).