Golden test for Closed Key Registration

[curiecrypt]

Content

This PR includes golden test for the Merkle tree batch commitment of the closed key registration.

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • CHANGELOG file is updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • All check jobs of the CI have succeeded
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested

Comments

Issue(s)

Relates to #2880

[github-actions]

Test Results

    4 files  ±0    169 suites  ±0   22m 2s ⏱️ -7s
2 293 tests +1  2 293 ✅ +1  0 💤 ±0  0 ❌ ±0 
7 201 runs  +3  7 201 ✅ +3  0 💤 ±0  0 ❌ ±0 

Results for commit 20f3aeb. ± Comparison against base commit 40f7bdf.

[Copilot]

Pull request overview

This PR adds a golden test to verify the serialization and deserialization of the Merkle tree batch commitment for closed key registration. The test ensures that the serialization format remains stable across versions.

Key Changes

• Added golden test module with serialization/deserialization verification for MerkleTreeBatchCommitment in the closed key registration flow
• Bumped version from 0.9.1 to 0.9.2
• Updated CHANGELOG to document the new golden test

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
mithril-stm/src/protocol/key_registration.rs	Adds new golden test module with golden_value() helper and golden_conversions() test to verify serialization consistency of Merkle tree batch commitment
mithril-stm/Cargo.toml	Updates version from 0.9.1 to 0.9.2
mithril-stm/CHANGELOG.md	Adds entry for version 0.9.2 documenting the new golden test
Cargo.lock	Updates version reference to match Cargo.toml change

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[jpraynaud]

LGTM 👍