feat: multi-protocol trait + Aave V3 on Ethereum + bps margin profit gate

[obchain]

Summary

Three coupled changes that ship v0.2 of the bot. Tight coupling means they share config.rs and cli/main.rs edits — splitting them now would be artificial. They are reviewed as one unit but the body below treats each theme separately.

1. min_profit_margin_bps replaces the absolute USD floor

The old min_profit_usd_1e6 = $5 floor scaled poorly: loose on small trades, meaningless on large ones. Replaced with a basis-points margin gate:

gross_swap_output_wei >= total_cost_wei * (10_000 + min_profit_margin_bps) / 10_000

• Default 1000 bps (10% margin), validated <= 10_000.
• Drop reason BelowMinMargin.
• Fork profile lowers to 100 bps for demo staging.
• crates/charon-core/src/profit.rs:315, config.rs:303.

2. LendingProtocol trait + ProtocolKind factory

Pipeline now holds Arc<dyn LendingProtocol> and never names a concrete adapter. ProtocolKind enum is #[non_exhaustive] so adding variants is non-breaking. Factory in charon-protocols/src/lib.rs matches on the kind and returns a trait object.

VenusAdapter migrated to impl LendingProtocol unchanged behaviourally. Scanner, executor, profit calc, queue, simulator, submitter, metrics emitter, and Grafana dashboard are protocol-agnostic.

• crates/charon-core/src/traits.rs:59 — trait
• crates/charon-core/src/config.rs:588 — ProtocolKind enum
• crates/charon-protocols/src/lib.rs:52 — factory

3. Aave V3 adapter + Ethereum support

AaveV3Adapter implements LendingProtocol against the Aave V3 Pool and PoolDataProvider. Reuses the lenient getReserveData decoder (PR #421) so Ethereum's 15-field tuple parses cleanly alongside BSC's truncated 12-field one.

CharonLiquidatorAave.sol is the on-chain twin: flashLoanSimple → Pool.liquidationCall → Uniswap V3 exactInputSingle → repay Aave + 5 bps premium → sweep residual to immutable cold wallet.

• config/fork-eth.toml — Ethereum fork profile pinned at block 20459016 (Aug 5 2024 yen-unwind cascade).
• deploy/compose/local-stack-eth.yml — Prometheus on 127.0.0.1:9093, Grafana on 127.0.0.1:3001 so BSC and ETH stacks run side-by-side without collision.
• crates/charon-protocols/tests/aave_v3_{connect,fetch}.rs — integration tests against a live anvil ETH fork; both pass.

Demo numbers (reproducible)

FORK_RPC=https://eth.drpc.org FORK_BLOCK=20459016 FORK_CHAIN_ID=1 \
  CHARON_SKIP_DEV0_NONCE_RESET=1 ./scripts/anvil_fork.sh

# wipe slot, deploy CharonLiquidatorAave (see Notion walkthrough)

CHARON_SIGNER_KEY=0xac0974...0ff80 \
CHARON_PRICE_MAX_AGE_SECS=63072000 \
./target/release/charon --config config/fork-eth.toml replay \
  --protocol aave_v3_eth --block 20459016 \
  --borrower-file /tmp/seed-eth.txt --hold-secs 600

emits 2 / 4 seeded borrowers, total predicted net profit $14,538.74:

Borrower	Debt → Collateral	Predicted profit
0x99E881…5Ddc3	DAI → WETH	$7,687.01
0x66466…36DE5	DAI → WETH	$6,851.73
0xe6a5e9…9da4	USDT → LINK	dropped (debug pending)
0xd8cd65…566b	USDC → WETH	dropped (debug pending)

The two silent drops between profit gate and queue are tracked as a follow-up.

Test plan

• cargo build --release passes
• cargo test --workspace passes
• cargo test -p charon-protocols --test aave_v3_connect passes against ETH fork at 20459016
• cargo test -p charon-protocols --test aave_v3_fetch passes against ETH fork at 20459016
• BSC × Venus replay at block 91323624 still emits 4 / 4 with $39,524.48 (regression check)
• ETH × Aave V3 replay at block 20459016 emits 2 / 4 with $14,538.74
• Grafana ETH stack on :3001 renders: positions-by-bucket, queue depth, profit cumulative
• Adding a third chain × Aave V3 (e.g. BSC × Aave V3) requires only TOML — verified by reading factory code path