feat(governance): v0.0.28 origin-chain-governance pallet scaffold (Phase 5.1 Foundation Treasury CHN-4)

Phase 5.1 GOVERNANCE pallet scaffold canonical. Reemplaza placeholder
GovernanceConfig stub en existing origin-chain-governance crate con real FRAME
pallet. AI-Driven Human-Guarded canonical CHN-4 — 5 AI advisor agents ADVISE
only, humans-only vote canonical non-negotiable.

## Pallet surface canonical

- Pallet<T> + Config trait + RuntimeEvent
- Proposal struct (11 fields content-addressed via BLAKE2-256)
- ProposalStatus enum (Voting + Approved + Rejected + Withdrawn)
- Proposals<StorageMap<ProposalId, Proposal>> per-proposal O(1)
- Votes<StorageDoubleMap<ProposalId, AccountId, VoteStance>> double-vote prevention
- Events ProposalSubmitted + VoteCast + ProposalFinalized
- Errors 8 variants (ProposalNotFound + AlreadyVoted + VotingPeriodClosed/Open + StakeInsufficient + ProposalAlreadyFinalized + AdvisorMayNotVote + ProposalIdCollision)
- Scaffold dispatchables submit_proposal + cast_vote + finalize_proposal
- Helper derive_proposal_id via BLAKE2-256 hash (Inmutable #16 byte-determinism)
- sp_api::decl_runtime_apis! GovernanceApi declaration (query_proposal + query_vote)

## Types canonical updated

- origin-chain-types/src/governance.rs: added scale derives a ProposalId + VoteStance + Vote (Encode + Decode + DecodeWithMemTracking + MaxEncodedLen + TypeInfo) para FRAME-compatibility canonical

## Files

- EDIT: crates/origin-chain-governance/Cargo.toml (stub → FRAME pallet deps canonical)
- REPLACE: crates/origin-chain-governance/src/lib.rs (placeholder → ~360 LOC scaffold)
- EDIT: crates/origin-chain-types/src/governance.rs (scale derives canonical)
- EDIT: CHANGELOG.md (v0.0.28 entry)

## Verification

- cargo test -p origin-chain-governance — 5 tests verde, 0 failures
  (pallet_compiles + derive_proposal_id deterministic + different + status variants + re-export)

🏛️ Phase 5.1 scaffold canonical. Wire pattern v0.0.29 next.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -2212,7 +2212,15 @@ dependencies = [
 name = "origin-chain-governance"
 version = "0.0.1"
 dependencies = [
+ "frame-support",
+ "frame-system",
  "origin-chain-types",
+ "parity-scale-codec",
+ "scale-info",
+ "sp-api",
+ "sp-core",
+ "sp-io",
+ "sp-runtime",
 ]
 
 [[package]]