Architecture] Implement Multi-Collection Creator Revenue Split Protocol Contract Extension

[Darkvader-ship-it]

Estimated Effort: 4 weeks / 7 days

Impacted Subsystems / Files:

• contracts/phase-protocol/src/lib.rs
• app/api/market/[id]/offers/[offer_id]/route.ts

Context & Problem Statement:
Currently, settle() in contracts/phase-protocol/src/lib.rs executes a fixed 95% creator / 5% protocol treasury split. Complex creator entities, co-artists, and DAOs cannot split settlement proceeds automatically on-chain, requiring insecure manual redistribution off-chain.

Technical Requirements & Scope:

1. Add CollectionShares struct to contract storage mapping payee addresses to basis points (total 10,000 BP).
2. Update create_collection to accept optional Vec<(Address, u32)> share definitions.
3. Refactor settle() to iterate over payee shares and transfer exact stroop amounts atomically.
4. Ensure treasury 5% fee split occurs prior to creator share distribution.

Multi-File Change Surface:
Requires breaking contract signature changes in contracts/phase-protocol/src/lib.rs, updating buildCreateCollectionTransaction and buildSettleTransaction in frontend UI, and updating API routes.

Acceptance Criteria:

• On-chain settlement distributes funds atomically to up to 10 co-creator addresses.
• Transaction fails gracefully if total payee basis points do not sum to 9,500 BP.
• Emits collection_shares_settled event with array of payouts.

Suggested Approach / Investigation Steps:

1. Define CollectionShares contract type and storage DataKey.
2. Update settle() Rust function with split loop and arithmetic overflow checks.
3. Modify UI collection creation modal in components/dashboard/ to configure splits.

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