feat(cbc): cooperative batch clearing module over house vaults

[JaeLeex]

Summary

• Add nunchi-cbc: uniform-price cooperative batch clearing (PRD in PRD: Hybrid AMM design — house + CBC + off-chain bin manager #119). Signed intents from house vaults and allowlisted MMs rest in per-market queues; the keeper closes batches; all executable fills clear at one deterministic price and settle through nunchi-house's checked clearing API.
• Price discovery maximizes executable volume over intent limit prices plus the oracle price, so batches clear exactly at oracle whenever it sits inside the volume-maximizing range (matches the PRD worked example); ties break toward oracle, then lower. Out-of-band prices record OutsideBand and leave the queue untouched.
• Buy intents reserve worst-case quote (limit × qty) in the house module at submission — a vault can never distort the batch price with intents it cannot settle. Allocation walks submission order; each matched chunk validates both sides against live house state (mode gates, reducing capacity, caps, leverage) and settles immediately, so settlement is conservation-preserving by construction.
• Intents rest across batches (partial fills stay pending), reduce-only quantities cap against inventory, and batch results (outcome, prices, aggregate fills, retired intents) are the queryable event surface for ABM reconciliation.

Trust seams (documented in README)

• Keeper posts the oracle price per clearing call — interim seam until oracle-module wiring; this is why CloseAndClearBatch is keeper-gated, not permissionless.
• Sell intents post no collateral (bounded by notional caps + house exposure checks); economic short margining arrives with perps wiring.
• KKT risk-weighted clearing (gamma/c) is the v1.1 price-rule upgrade.

Test plan

• cargo test -p nunchi-cbc (11 tests, including the PRD worked example end-to-end: house +1,200 long sells vs two MM bids → clears 1,000 @ oracle 10,000, house left +200 PartiallyFilled, quote conserved across free+reserved balances)
• cargo check --workspace --all-targets
• cargo check -p nunchi-cbc --no-default-features
• cargo clippy -p nunchi-cbc --all-targets -- -D warnings

Stacking

Base is jae/house-module → #119 → #117. This completes the on-chain half of the hybrid AMM stack; the ABM stays off-chain per the PRD.

[codecov]

Codecov Report

❌ Patch coverage is 68.05556% with 391 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cbc/src/rpc.rs	0.00%	144 Missing ⚠️
cbc/src/ledger.rs	80.00%	64 Missing and 64 partials ⚠️
cbc/src/types.rs	75.89%	7 Missing and 47 partials ⚠️
cbc/src/genesis.rs	0.00%	35 Missing ⚠️
cbc/src/transaction.rs	78.88%	9 Missing and 10 partials ⚠️
cbc/src/db.rs	87.91%	10 Missing and 1 partial ⚠️

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