feat: key merge voting and holder position migration

[Emmazlee]

Overview

creator-keys/src/acl_limits_merge_sunset.rs shipped only a placeholder key-merge flow: propose_key_merge stored a ratio and execute_key_merge flipped flags and returned the ratio. There was no way for source-key holders to vote, no threshold check, no balance migration and no source-key deprecation, so the merge was a no-op. This change builds the missing voting, migration and deprecation flow inside the existing module (the crate still has no matching lib.rs entrypoints) and reuses the protocol's real holder-balance storage.

Related Issue

#962 — Add on-chain key merge voting and execution with position migration.

Changes

• [ADD] creator-keys/src/acl_limits_merge_sunset.rs — vote_on_merge(holder, source_key, approve) weights a source-key holder's vote by their liquid KeyBalance, replaces a previous vote by removing the old weight before adding the new one so no holder is double counted, and rejects non-holders and votes cast after execution.
• [ADD] MergeVoteRecord and MergeMigrationEntry contract types, the MergeHolders / MergeVote / MergeMigrationLog keys in the module's existing EmwulrdDataKey namespace, and get_key_merge_proposal / get_merge_migration_log views.
• [CHANGE] KeyMergeProposal now carries approval_threshold_bps, votes_for, votes_against and total_voted_weight.
• [CHANGE] propose_key_merge takes the approval threshold and the source-holder set, validates the ratio/threshold ranges, rejects duplicate holders and refuses to overwrite an executed proposal.
• [CHANGE] execute_key_merge validates the weighted approval share against approval_threshold_bps before touching state, then migrates every registered holder's liquid and staked positions to the target key at conversion_ratio_bps (target balances are additive), transfers the aggregate TotalStaked, stores the full migration log, deprecates the source key with the protocol-wide marker plus the module sunset status, and emits MergeExecuted with the ratio/counts and KeyDeprecated.
• [ADD] Five #[test] cases covering weighted vote collection, non-holder rejection, vote switching without double counting, threshold failure with no state mutation, and the successful migration/deprecation path including the second-execution guard and invalid proposal inputs.

Verification Results

I fetched creator-keys/src plus the workspace manifests into a scratch tree and compiled it against the repo's pinned soroban-sdk 22.0.11 with cargo check --offline --tests and cargo test --offline --lib acl_limits_merge_sunset::test. Both succeed; the five new tests pass:

running 5 tests
test acl_limits_merge_sunset::test::propose_rejects_duplicate_holders_and_bad_parameters ... ok
test acl_limits_merge_sunset::test::changing_vote_replaces_weight_without_double_counting ... ok
test acl_limits_merge_sunset::test::merge_votes_use_liquid_source_balance_as_weight ... ok
test acl_limits_merge_sunset::test::execute_rejects_below_approval_threshold ... ok
test acl_limits_merge_sunset::test::execute_migrates_all_positions_and_deprecates_source ... ok

test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 378 filtered out

lib.rs was left untouched, and I did not run the crate's wider snapshot suite.

Acceptance Criteria	Status
Votes collected correctly from source key holders	✅ merge_votes_use_liquid_source_balance_as_weight — weight equals the holder's liquid source-key balance
Execution rejected below vote threshold	✅ execute_rejects_below_approval_threshold — returns Unauthorized, balances untouched
All holder balances migrated at correct conversion ratio	✅ execute_migrates_all_positions_and_deprecates_source — liquid and staked moved at 50%
Source key deprecated atomically post-migration	✅ Same test asserts the deprecation marker and sunset status
Unit tests cover vote collection, threshold failure, and successful migration	✅ Five tests in acl_limits_merge_sunset::test

Closes #962

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@Emmazlee Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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